Henry Clay is the nominee.
Not necessarily. To recycle an old soc.history.what-if post of mine:
***
(1) 1840 election--the 1839 Whig convention is often looked at as a
Harrison versus Clay contest, but in fact Scott for a while seemed to have
reasonable prospects of getting the nomination. He had won enormous
popularity in western New York in particular, not only for his role in the
War of 1812, but for the way he had helped defuse US-Canadian tensions in
the late 1830's. After several ballots, there were 96 votes for Clay, 91
for Harrison, and 68 for Scott. Thurlow Weed had gotten Connecticut to
switch from Clay to Scott, and was preparing to approach some delegates
from the South, where he knew there was some Scott sentiment, especially in
North Carolina and Virginia.
Unfortunately for Scott, Harrison's supporter Thaddeus Stevens beat Weed to
the punch. Stevens had somehow obtained a letter that Scott had written to
Francis Granger of New York in a clumsy bid to attract antislavery support.
Stevens showed the letter to the Virginia delegates, and it had the
expected effect: the Virginians dropped all talk of switching to Scott,
and made it clear that if they deserted Clay, it would be for Harrison. As
soon as Weed realized Scott would get no Southern support, he swung the
votes he commanded into the Harrison camp to finish off Clay.
Without a Granger letter, it is at least conceivable that Scott would have
gotten the nomination, and if so he would, for all his weaknesses as a
candidate, almost certainly have defeated Van Buren, given the latter's
unpopularity in 1840. Another thing that could have made Scott the
nominee, even with the Granger letter: have Harrison, who after all was
already 66 years old in 1839, die in that year instead of 1841. Scott then
becomes the Northern Whigs' alternative to Clay. If nominated, he might
have more trouble in the South than Harrison in OTL, but he could still
probably beat Van Buren.
The likely consequences of a Scott victory in 1840 are the same as that of
just about any other Whig than Tyler holding the White House in those
years: the Whig nationalist economic program (tariffs, national bank,
internal improvements) is enacted and not vetoed; the Whigs claim credit
for the economic recovery that starts in 1843; the country divides more
along economic philosophy than regional/slavery lines; the extremely
divisive Texas issue (and therefore the Mexican War) is at least postponed.
https://groups.google.com/d/msg/soc.history.what-if/0rnkWwBHUD8/ShGfRsTHQ8oJ