Hypothetical US Presidential Election, 1848: Polk seeks a second term.

[The Mikado]

Is the question who wins or who would I vote for?

Polk was an ill man anyway and even if he weren't, van Buren would undermine him considerably in the North just like he did to Cass. I have Polk winning by a very narrow margin, probably in a "Polk wins the electoral vote but loses the popular vote" scenario, by swinging Pennsylvania, Georgia, Tennessee, and perhaps Delaware and Maryland. i suspect Polk would've signed the Compromise of 1850 and been a terrible president in his second term as a result.

Van Buren would've been best, obviously, and if I were voting in New York or something he'd have my vote, but if I were in a swing state like Pennsylvania I might consider voting for Taylor. If Zachary Taylor hadn't died when he did he could've actually done a lot of good. The man might've been a southern slaveholder, but he was firmly committed to the US and had zero tolerance for secessionists, and his opposition to the Compromise of 1850 might have just provoked a premature and half-hearted Southern rebellion crushed at swordpoint by a Southerner that would've put the South in a much harder bargaining position.