DBAHC: Whig party disappears, Democrats remain until today.

Present day American politics is mostly dominated by a two party system with the Whig Party and the People's Party. This wasn't always the case, though. The Democratic party was a major party opposed to the Whigs, but it ultimately fell apart and was later replaced. This challenge has two parts. First, the Whig party has to disappear. Second, the Democratic party has to survive to the present day as a major party. What party would replace the Whig's if this happened, and what would they and the Democratic party believe today?
A good POD could be the Democrats not becoming the "party of the South" with the Democratic Party becoming "tainted" by association with the attempt by the South to secede while the Whigs were the "party of Unity".