Let’s say Al Gore beat George Bush in 2000 and went on to lose re election to Senator John McCain in 2004. McCain goes on to win re election in 2008 against Senator Hillary Clinton.
Obama wins the 2012 democratic nomination against Bernie Sanders who comes in a distant second but still won New Hampshire and a few other states.
Who will win the general election?
I imagine if the economy didn't crash in 2008, it would've in 2009 or 2010 and with economics not being McCain's strong suit I imagine 2010 and 2012 are massive Democratic wave years, so Obama likely wins and with more experience under his belt (assuming he's still elected to the Senate in 2004 and serves a full term) likely wins by more than OTL.