Here is what the latest polls show:
In a general-election match-up among registered voters, McCain is 2 points ahead of Obama, within the margin of error; he beats Clinton by 6 points.
McCain runs ahead of Obama on every issue except health care. The Arizona senator has a 13-point advantage on Iraq and a 37- point lead on terrorism. He also does better on managing the economy. One area where Obama has a clear edge is on the question of who would bring the most change in Washington; the Illinois senator has an almost 3-to-1 lead.
When it comes to who has the right experience to lead the nation, McCain has a 12-point lead over Clinton, compared with a 31-point advantage over Obama.
In another sign of strength for McCain, more than half of Republican voters say they are happy with him as their nominee, including a majority of conservatives.
Independents appear to be a significant problem for Clinton in a general election. While she has strong favorable ratings from Democrats, at 82 percent, just 48 percent of independents agree. Obama has a 63 percent favorable rating among independents, while McCain has a 65 percent positive rating.