An old soc.history.what-if post of mine:
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Was James Buchanan a great or only a near-great president? Historians
continue to debate the question, but it would be foolish to underrate his
accomplishments.
Let's review how Buchanan was elected president: In 1844 Van Buren had a
majority of delegates nominally supporting him at the Democratic national
convention but enough of them voted to re-impose the two-thirds rule that
he had no chance to gain the nomination. Lewis Cass, a Westerner, ardent
expansionist, and favorite of the "soft money" Democrats, was the obvious
alternative, but because it was the Cass men who had initiated the drive
to block Van Buren with the two-thirds rule, the Van Burenites were
bitterly determined that he not be nominated. For a while, there was some
talk of nominating a "dark horse," James Knox Polk of Tennessee, but Polk,
who was a loyal Van Buren supporter despite his disappointment with Van
Buren's stance on Texas, refused to be a candidate. (I have often
wondered if Polk and the convention might have decided differently if
General Jackson, known to be a Polk supporter, had not died earlier that
year.) Eventually the convention turned to James Buchanan of
Pennsylvania, who like Cass was a bit too conservative on economic issues
for hard-core, hard-money Van Burenites, but won their support by agreeing
to revive the Independent Treasury. In any event, despite his having been
a Federalist in his youth, he was less obnoxious to the Van Burenites than
Cass was. In the general election, Buchanan, promising the "reoccupation
of Oregon and the re-annexation of Texas, at the earliest practicable
period" narrowly defeated the Whig candidate Henry Clay. (Buchanan did
lose a few Southern states which a Southern Democratic candidate might
have carried--notably Georgia and Louisiana--but narrowly carried the key
Northern states of New York and Pennsylvania. In New York, he was helped
by the Liberty Party splitting the anti-Texas vote, and by the Van
Burenite Silas Wright's gubernatorial candidacy. In Pennsylvania, of
course, he was helped by his "native son" status; indeed I am by no means
certain that any other Democratic presidential candidate would have
carried the state.)
Buchanan's most important accomplishments as president are too familiar to
require extended discussion: the compromise that divided Oregon, and the
Mexican War which got the US the Southwest. There are, however, some
other decisions of his that deserve attention, because they show his
political shrewdness. He resisted the cries of dogmatic "strict
constructionists" to veto the rivers and harbors bill; he knew that to do
so would only further enrage Northwesterners disappointed by his
"timidity" on Oregon. He also resisted cries by some Southern free
traders for a massive reduction in the tariff; as a Pennsylvanian he knew
that this would hurt the Democrats badly in that state. The result was
that in the 1846 elections, despite some dissatisfaction with the war, the
Democrats were able to maintain control of both houses of Congress.
Perhaps the most unappreciated aspect of Buchanan's presidency was his
resolution of the problem of the status of slavery in the newly acquired
Mexican cession. Buchanan at an early stage came out in favor of
extending the Missouri Compromise line to the Pacific. (In this, he
disagreed with Secretary of State Cass, who instead favored something
called "popular sovereignty" under which the people of each territory
would themselves decide the status of slavery. Buchanan thought that this
would merely encourage conflicts between pro- and anti-slavery settlers in
each territory. A handful of squatters had no right to determine
something that was of interest to the nation as a whole.) Southerners--
whether Democrats or Whigs--almost unanimously agreed with Buchanan's
policy in this area. (True, a few thought that government prohibition of
slavery in *any* territories was unconsitutional, but for the most part
they dismissed this as a purely abstract question, since they didn't
expect slavery to flourish north of 36° 30' anyway, and since extension of
the line would set a precedent for having slavery in any future territory
the US might acquire in Latin America or the Caribbean.) Getting 36° 30'
through the Senate was relatively easy, but in the Northern-majority
House, Buchanan had to use all the patronage and pressure at his disposal
to convince just enough Northern Democrats (in combination with a
virtually solid South) to pass his plan.
So why did historians once tend to rank him as only a near-great rather
than a great president? Well, some of them had been brainwashed by the
Whig and Abolitionist propaganda about the Mexican War being an evil war
of aggression. (Though I notice that few people who argue this way
actually want to give San Francisco or Los Angeles or Santa Fe or
Monterrey back to the Mexicans.) And of course some people still argue
that Buchanan's policies gave slavery a new lease on life, enabling it to
last until 1900 (and black "apprenticeships" to last a couple of decades
longer). But realistically, how could slavery have been abolished much
earlier (except perhaps through a bloody civil war, but nobody really
advocates *that*, and anyway I can't see how the North could win such a
war, since Great Britain was so dependent on Southern cotton that she
would be sure to intervene)?
Buchanan was of course way too controversial to be re-nominated in 1848
under the two-thirds rule but today we should appreciate him--as an
increasing number of historians do--as one of America's truly great
presidents.
https://groups.google.com/d/msg/soc.history.what-if/-68iurHBur0/tHCcUE1bD-UJ
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In that post, I had Buchanan nominated and elected instead of Polk (my POD is having Polk's most important supporter, Andrew Jackson, die early), and had him choose policies similar to Polk's but with two exceptions: (1) he doesn't alienate the North by vetoing the rivers and harbors bill
https://en.wikipedia.org/wiki/Rivers_and_Harbors_Bill or by decreasing the tariff as much as Polk did in OTL; and (2) he comes out squarely in favor of territorial division on the Missouri Compromise Line (something he advocated as Secretary of State in OTL) and manages to implement it (I'll admit that getting it through the House will be hard, but if he manages to retain a Democratic majority there and to use patronage adroitly it is not inconceivable--he *almost* got the Lecompton Constitution through an even more northern-majority House years later in OTL, after all) so that the doctrine of "popular sovereignty" which bore such disastrous results in Kansas, never becomes widespread...
(Note that I also have the US expand a little further into Mexico than in OTL, with my reference to Monterrey.)