Fuller details the transformation of the National Era into a Pro-Annexation paper to illustrate this change to which Hatcher speaks of....
The New York Herald also at this time that "The abolitionists will scarcely offer it a serious opposition. Mexico will all be free, and consequently the North will have no interest in opposing her annexation."
The New York
Herald, a notoriously sensationalistic newspaper, was hardly a reliable source. It was an All Mexico journal in a part of the country where Wilmot Proviso sentiment was strong (among Democrats as well as Whigs) and so of course it had an interest in claiming not only that there was no danger of slavery going into Mexico, but that even northern antislavery Whigs agreed with the newspaper on this and secretly favored All Mexico. This was characteristic of the northeastern penny press as a whole--for example, the New York
Sun spread a false report that John Quincy Adams favored the acquisition of All Mexico as an antislavery move (whereas actually Adams was against annexing
any Mexican territory). These northeastern Democratic newspapers by the way were almost the only people who paid much favorable attention to Gamaliel Bailey and the
National Era's "Plan of Pacification and Continental Union." Bailey's fellow antislavery northern Whigs thought it was chimerical or even "pandering" to the spirit of conquest.
In any event, I find it impossible to see any "all Mexico" plan that could get a majority in Congress. Let's look at two diametrically opposed alternatives: (1) Bailey's plan, and (2) the plan of one of the few southern supporters of All Mexico, Henry Foote of Mississippi.
(1) Bailey's plan: The US should declare peace, and send invitations to each Mexican state to join the United States--presumably with their antislavery laws intact. The Mexican states accept and suddenly the South is surrounded by free states on all sides!
Now there are a number of reasons why I think this plan could not possibly come to pass. For one thing, the Mexican states--whose genuine, unpressured agreement Bailey insisted would be required--would be most unlikely to agree. (And yes, that goes for the Puros, too, or even especially. As I wrote elsewhere, "I notice that to support your contention that the Puros favored annexation, you cite p. 215 of Pedro Santoni,
Mexicans at Arms: Puro Federalists and the Politics of War, 1845-1848 who quotes Colonel Hitchcock and Commissioner Trent to this effect. But consider what Santoni writes just three pages later!: 'The opinions of contemporary observers like Colonel Hitchcock and Trist about the puros are also flawed. They failed to recognize the factionalism—which puzzled many politically conscious Mexicans—within the party in late 1847. For example, moderado leader Mariano Rica Palacio commented that he did not understand the double conscience of the puro party, in Mexico in favor of annexation and in Queretaro for a war without respite."65 Although some of Gomez Farias' backers harbored annexationist ideas as 1847 came to an end,
most puros followed Gomez Farias' leadership. [my emphasis--DT] Gomez Farias' contingent made every effort to insure that hostilities continued with the United States to avoid what they considered to be a dishonorable peace. Gomez Farias' Yankeephobia, in fact, remained as resolute in the fall of 1847 as in the more visionary days of 1845...'") Second, as noted, Bailey failed to convince most of his fellow Whigs, even in the North, of this idea. (Even if they were convinced that annexed Mexican territory would not support slavery, one should remember that opposition to slavery was not the
only reason Whigs tried to prevent or at least limit territorial expansion.) Third--and this is what makes Congressional consent for this plan impossible even if the first two obstacles are somehow removed--southerners, whether Democrats or Whigs, would unanimously oppose this idea. Even if the South stood alone in opposing it, they would have half the Senate against it! And they would not stand alone, in any event; a good many northerners, especially Whigs, would still oppose the idea.
(2) Henry Foote's plan is the only all-Mexico policy that would have
some southern support:
"Foote agreed, arguing before the Senate that Mexico should be annexed and divided into territories in the traditional American manner and that, after a period of "gradual civilization and Americanization," the Mexican territories might become states. He was clear to maintain, however, that before this process took place, the United States should establish a list of priorities, at the top of which included "securing the mining districts from encroachment from a, quarter, the introduction of our system of import duties," and the declaring of millions of acres in Mexico "public lands," which would be open to American settlement and commercial exploitation. Foote's arguments before the Senate also made it clear that, while former Mexican provinces might become states under his plan, true control of Mexico would remain Anglocentric to create a "perfect social order throughout the whole extent of the region."
https://books.google.com/books?id=hHJyDwAAQBAJ&pg=PA95
This plan at least would have some attractions to Southerners. No need to worry about dark-skinned antislavery voters dominating the US, because the Mexican territories would not be admitted to the Union until they had been Anglo-Saxonized. There would even be the chance to introduce slavery into Mexico unless the Wilmot Doctrine was introduced and upheld by the Supreme Court (True, it could be argued that even without the Wilmot Proviso the Mexican laws against slavery would remain in force ; but some southerners already hoped and some northerners feared that the Supreme Court would find such laws unconstitutional as a denial of the right of slaveholders to bring their human "property" into the territories; as indeed it did some years later in the
Dred Scott case.) But in the first place, not even all Southerners would accept the idea. Sure, if removal of the Indians and Mestizos and "Anglo-Saxonization" of the heavily populated areas of Mexico could be accomplished, they might favor it But removing millions of Mexicans would be immeasurably more difficult than removing 16,000 Cherokees. As a recent study has concluded, "All Mexico failed to garner much southern support because few believed forced removal was plausible. Therefore, the United States would be stuck with lands populated by “undesirable” races. The editors of the Pensacola Gazette countered All Mexico proponents by explaining that Mexicans were “not ripe for the blessings which we would confer upon them- the blessings of wise laws and a stable government.” The paper asked readers: “What shall we do? Carry on the war until we force them to be happy?” The nightmare of acquiring a large, mixed-race population would be a frightening reality if supporters of All Mexico had their way. Not only were the Mexicans not enslaved, they had already shown with their guerrilla tactics that they would not docilely submit to American rule. A North Carolina newspaper editorial opined that such an acquisition would “cost our Government a great deal of trouble and money, and, after all, what do we gain? A bankrupt country, with three millions of whites and five millions of stark-naked Indians to be supported.” When Secretary of State James Buchanan advised President Polk that the United States ought to secure the territory as far south as Tamaulipas, even Polk “expressed a doubt as to the policy or practicability of obtaining a country containing so large a number of the Mexican population.” Throughout the war the wholehearted belief by most southerners in the intellectual and moral inferiority of the Mexicans continued, and the thought of extending the liberties of the Constitution to them aroused concern in the South. Representative Edward Cabell of Florida doubted the “black, white, red, mongrel, miserable populations of Mexico- the Mexicans, Indians, Mulattoes, Mestizos, Chinos, Zambos, Quinteros” could ever become “free and enlightened American citizens.”57 Underlying these racist attacks of the All Mexico movement, of course, were fears for the southern social order."
https://research.libraries.wsu.edu/...ll_wsu_0251E_11346.pdf?sequence=1&isAllowed=y
Second, even if Foote's idea could get unanimous support from southern Democrats (which it could not) it would be doomed by unanimous opposition from the Whigs. That northern Whigs would oppose it is obvious; and so would southern ones, as the quote from the Whig congressman Edward Cabell of Florida, cited above, makes clear. Southern Whigs did not believe that Mexico could be "redeemed" for the Anglo-Saxon race for a long time to come. In any event, though the Whigs by themselves were strong enough to block All Mexico in the House, they would probably be joined by many Democrats who wanted some territorial acquisitions from Mexico, but thought this was going too far...
(Of course there is another obstacle to either of these plans being approved; Polk would not support either of them, in part because he knew the opposition they would arouse but also in part because he was never an All Mexico man, even if his anger over the Mexican rejection of his initial offer made him for a while desirous of getting further territorial acquisitions from Mexico.)