From an AP/Yahoo poll:
In last November's Associated Press-Yahoo News poll, people preferred an unnamed Democratic White House candidate to a Republican contender by 40 percent to 27 percent. In this month's survey, McCain was essentially tied with the two Democratic rivals: It was McCain 37 percent to Hillary Rodham Clinton's 36 percent, and McCain 36 percent against Barack Obama's 34 percent….
Overall, 57 percent in this month's AP-Yahoo poll found Barack Obama likable, compared with 47 percent who said so about John McCain and 37 percent who thought so about Hillary Rodham Clinton. That's an increase since November of 8 percentage points for McCain and 6 points for Obama, while Clinton is 3 points lower.