John McCain has confirmed he's going to run for president. The Republican senator from Arizona mounted a surprisingly strong challenge to George W Bush for the party's nomination in 2000, and since then has been one of the most prominent figures in American politics.
McCain's just about the strongest contender from either party for the presidency. He's rightly admired by supporters on both sides for his record of crossing partisan barriers to push for moderate laws on issues such as campaign finance and getting rid of torture. He's also done well to keep his mouth shut about the manner of his bitter defeat to Bush in 2000, when Dubya's team resorted to the dirtiest of dirty tricks to ensure their man won.
Two big things count against him. The main one is his continued support for sending more American troops to Iraq. The President might agree with him, but they're two of the very few who still think that's a good idea. Then there's his age. If he's elected, McCain will be, at 72, the oldest man ever to enter the White House.
Current polls put him behind Rudy Giuliani among Republicans, which is probably why McCain's decided to get his face out there a bit more, and announce his candidacy on the David Letterman show. Over the next weeks and months it would be a big surprise if he didn't re-establish himself as the clear frontrunner for both his party's nomination, and the presidency itself.