No reason for any change. W/o the war, the election is on domestic policies only. and Wilson's were popular.
But one reason they were popular in OTL was the prosperity induced in part by war orders. In 1913-14 Republicans had some success in blaming the recession on Wilson's "anti-business" policies and the Underwood Tariff. This argument faded as prosperity returned. When Hughes in 1916 claimed the US was living in a "fool's paradise" and needed higher tariffs to counter a flood of imports from Europe once the war ended, he got little response because he was in effect conceding that for now the economy was prosperous. So how well Wilson would do in 1916 without the war might depend on how rapidly and completely the US would recover from the recession. As I wrote elsewhere:
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Progressivism Dependent on Prosperity? TR on the 1914 Elections
Not exactly a what-if, but some thoughts prompted by reading John Allen Gable, *Theodore Roosevelt and the Progressive Party.*
1914 was a bad year for Progressives--with both a large and small "p." The Progressive Party did miserably, except for Hiram Johnson in California (whose victory was more a personal than a party triumph). More generally, it was a bad year for liberal reformers within the two major parties, as well as for third parties. The Old Guard was widely triumphant in the GOP. Joseph G. Cannon and William B. McKinley, old enemies of the insurgents, regained House seats lost in 1912. Boies Pentose, Reed Smoot, and others were re-elected to the Senate, and Warren Harding was elected senator from Ohio. In TR's own state of New York, the September primaries were bad news for progressives in all parties. Tammany candidates Governor Martin H. Glynn and Ambassador to Germany James W. Gerard overwhelmingly defeated the reformers John A. Hennessey and Franklin D. Roosevelt for the Democratic gubernatorial and Senate nominations, respectively. (This was the worst electoral defeat of FDR's career--much worse than 1920, both in percentage of the vote and because nobody blamed him for Cox's defeat.) In the GOP primary, standpatter James W. Wadsworth, Jr. was nominated for the Senate, while machine-backed Charles S. Whitman defeated the TR-backed Harvey D. Hinman for governor. In the general electiom, the Progressive candidate, Frederick M. Davenport, finished a poor fourth behind Whitman, Glynn, and impeached former governor Sulzer (who was runnng as a Prohibitionist and as candidate of his own "American" party--he had also unsuccessfully tried for the Progressive nomination).
https://en.wikipedia.org/wiki/New_York_state_election,_1914
Although the Demcorats did retain control of Congress, they lost many seats in the House to (generally conservative) Republicans. This was perhaps to be expected--many of the seats the Democrats had gained in the three-way race of 1912 could not be held under normal conditions--but was still interpreted as a trend to the Right.
Why the liberal debacle? The explanation given by TR and others is interesting. 1914 was a recession year--a recession the Republicans blamed on the Underwood Tariff and Wilson's alleged "anti-business" policies. (With regard to the tariff, TR partly agreed.) Eventually, the flood of war orders would help end the recession, but this was only beginning in November 1914. Contrary to the later belief fostered by the experience of the New Deal that depressions lead to liberal reforms (if not revolution), TR argued that progressivism depended on prosperity and could not thrive in hard times. (This was a widespread belief at the time, and a natural one, given that the Progressive Era, unlike the New Deal, was the child of prosperity, not depression.) Workers, said TR, "felt the pinch of poverty; they were suffering from hard times; they wanted prosperity and compared with this they did not care a rap for social justice or industrial justice or clean politics or decency in public life." As TR wrote in *The Outlook*:
"We cannot pay for what the highest type of democracy demands unless there is a great abundance of prosperity. A business that does not make money necessarily pays bad wages and renders poor service. Merely to change the ownership of the business without making it yield increased profits will achieve nothing. In practice this means that when the Nation suffers from hard times wage-workers will concern themselves, and must concern themselves, primarily with a return to good times, and not with any plan for securing social and industrial justice. If women cannot get any work, and nevertheless have to live, they will be far more concerned with seeing a factory opened in which they can work at night or work twelve hours every day than they are concerned with the abolition of night work or the limitation of hours of labor. Exactly the same is true of men. In the recent election in Pennsylvania the majority of the miners and wage-workers generally voted for the Republican machine, although this Republican machine had just defeated a workmen's compensation act, a child labor law, a minimum wage for women law, and various other bits of very desirable labor legislation. The attitude of the wage-workers was perfectly simple. They wished employment. They wished a chance to get a job. They believed that they had more chance if the candidates of the Republican machine were elected than they would otherwise have. Personally I very strongly believe that they were in error; but it was their belief that counted...."
https://books.google.com/books?id=gE1YAAAAYAAJ&pg=PA651
As Gable writes (p. 225), "Economically, he [TR] was expressing a concept held in common with many of his generation: that reform depended on what Walter Weyl called the 'social surplus,' the wealth produced by the nation over and above what was necessary to meet essential needs like food. The 'social surplus' could be used for social improvements and, as [Albert] Beveridge put it, to 'pass prosperity around.' But without such a 'surplus' men and women were forced to turn their attentions and energies to a struggle for the bare necessities, were prevented from pursuing humanitarian goals, blinded to the needs of others and to the commonweal. The concepts behind later Keynesian economics and the potentials of massive tax revenues for social improvements were largely absent from progressive thinking. The belief that prosperity and reform had to go hand in hand gave a certain ambivalence to progressive attitudes toward business, an ambivalence reflected in the policies of the Roosevelt and Wilson administrations alike, for capitalism was at once the threat to and the promise of the good life..."
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Anyway, if one assumes that the economy is as good in a peacetime as in a a wartime in 1916, I think that Wilson would not only get re-elected but perhaps by a larger margin than in OTL. IMO the war was (apart from prosperity) a net negative for Wilson in 1916. True, the "he kept us out of war" theme and TR's belligerence prevented the GOP from making as heavy inroads into the German- and Irish-American vote as they had expected--but they still made some, because some ethnic voters still thought that Wilson was too pro-British. To quote David Sarasohn,
The Party of Reform, pp. 228-230:
"Admittedly, Wilson did not suffer the kind of sweeping German and Irish apostasy that Democratic leaders had feared during the campaign. Nor were the losses universal; in some areas, such as St. Louis and Baltimore, German Democrats maintained their usual levels … But through much of the country, alienated ethnic Democrats, especially Germans, repudiated Wilson in numbers large enough to affect outcomes. "In the great majority of cases," reports Meyer Nathan on the Middle West, "Wilson either lost support among German Americans or did not gain support among them as substantially as he did among other voters."
"Looking at 110 midwestern counties with sizable German populations, Nathan found that in 44 of them Wilson ran worse in 1916 than he did in the three-sided contest of 1912, and in fifty-three he ran worse than Bryan had run in 1908 — at the same time that, in other counties, he was running ahead of all previous Democratic standards. These were counties that had been, in many cases, the backbones of Democratic strength in their area, counties where defeat or even narrow victory would be normally fatal to Democratic hopes statewide.
"Perhaps the most vivid example of Wilson's German defeats, and their costs, is provided by Wisconsin. The Democrats made a strong effort for the state, where they had elected a senator two years before and could count upon a strong appeal to labor, insurgent Republicans, and Milwaukee Socialists as well as the benign neutrality of La Follette. But, throughout the campaign, the warnings of rural German anger grew, and by election day the leaders knew the state was lost... traditionally an oasis of solid Democratic majorities in a Republican state, in 1916, German areas suddenly voted more Republican than the state as a whole.
"Democrats could count similar defections, with similar effects, in other states. New door in Minnesota, which Wilson lost by one-tenth of 1 percentage point the morning-after telegram from the state's Wilson volunteer chairman and simply, "Country German communities disappointing." He might have been thinking of Brown County, which had gone for Bryan in 1908 but now gave Wilson 31.6 percent, or Stearns, which had three times given the Commoner landslides (61.6, 61.3, and 56.8 percent) but now cast 54.4 percent of its votes for Hughes. Clifton Phillips notes German bolting from Wilson in Indiana, which he lost by less than I percent of the vote, and where one Democrat reported German ministers circulating anti-Wilson handbills. The Neu, York World suggested that German defections in the Fort Wayne area had hurt Wilson seriously, and the returns illustrate the point: Fort Wayne's county, Allen, one of the most German in the state, had voted thre times for Bryan, by increasing margins each time; now it went for Hughes, with a sharply increased Socialist vote....
"...The exception to Wilson's sweep of Ohio was what the
Cleveland Plain Dealer called "a surprising majority" for Hughes in Cincinnati's Hamilton County, where Wilson trailed the state ticket throughout the German wards.
"The defection of the urban Irish from the party of their fathers is more difficult to demonstrate. William O'Leary has argued that the Irish rebellion was insignificant, because Wilson carried the Irish wards and in fact ran better there than other Democratic presidenttial candidates had. But this is asking the wrong question. Democrats normally won (and needed, for any prospect of city or state victory) large majorities among the Irish, and for Wilson to run better in their wards than the aggressively pietistic Bryan or the hapless Parker would hardly be an indication of enthusiasm of very much use to him. In Chicago's 30h ward, the most Irish of the five Chicago wards O'Leary cites, Wilson did indeed win, with 58.5 percent of the vote. But the Democratic candidates for senator in 1914 and 1918 won 64 percent and 65.4 percent, respectively, and in elections for city clerk—a position in which the organization took a particular interest —the 30th ward went Democratic by 74.2 percent in 1913 and 77.5 percent in 1917.
"Wilson's difficulties appeared most vividly, and worse than had been expected, in New York City. With the treaty with Tammany, Democratic leaders had hoped for an old-time Democratic majority in the city, with the
New York World estimating a margin of 97,000. Instead, Wilson carried the city by less than 40,000, despite huge majorities in the Jewish districts. One source of his problems was evident: in the assembly districts with the highest Irish and German populations, the Democratic percentages dropped off notably from the assembly elections of the year before.
"The immediate reaction of many Wilsonians, who in the manner of reformers tended to vest their opposition with limitless reach and power, was that Tammany had knifed the president. Certainly, given the history of Wilson-Murphy diplomatic relations over the past four years, numerous Tammany tigers felt a coolness toward the Princetonian. But the machine defended itself persuasively. “The President got the top vote here in this city, as against a lesser vote for our own candidates, and he got a big vote," one New York leader wrote McAdoo. "Tammany could not control the Germans of its own party, whom Frank Cobb [editor of the
World] called every day agents of the Kaiser if they dared vote for any other save Wilson." Tammanyites also cited Wilson's similar difficulties across the river, in Frank Hague's heavily Irish and German Hudson County...."
One other point is that the war issue might have hurt Wilson among urban Progressives who were pro-British. Harold Ickes was to claim many years later that "I would have been for Wilson in 1916 if I hadn't been persuaded that his re-election would mean that England and France and all they had meant to our civilization might go to the dogs for all that we might do." (Ickes, *Autobiography of a Curmudgeon* [1937], p. 184)
(It has to be said, though, that the War was not the only problem Wilson had with Irish and German Catholics--his positions on Mexico and to a lesser extent on the Philippines probably also hurt him with Catholic voters.)
All in all, I think the War (leaving aside its effect on prosperity) cost Wilson votes--though surely not as many as the Democrats feared. But probably the War had little effect one way or the other on the Mountain and West Coast states, including California. The fighting seemed very far away there, ethnic votes were nor as numerous as in the East, and progressivism rather than peace was the major issue. This was recognized at the time: "While the East has been thinking in terms of the European war," explained Colorado Progressive leader Ed Costigan after the election, "the Progressives of the West have considered domestic peace and justice of greater importance, and have voted accordingly." Arthur Sears Henning,
Chicago Tribune political correspondent wrote "coming directly from the far west to New York City, I was struck immediately by the fact that I read next to nothing about Wilson having 'kept us out of the war.' The great conflict aborad is much more real to the people of the Atlantic seaboard than to the prairie states." Sarasohn, p. 220.