1.  Experience is not a plus when running for President: Don't believe me?  Look at recent history.  Al Gore and John Kerry both had more experience in government than George W Bush.  Bill Clinton beat handily George Bush Sr. and Bob Dole.  Dukakis was arguably less experienced than George Bush Sr., but he was the longest-serving governor in Massachusetts history.  There's just no indication that people look for the candidate with the longest resume.  

2.  Being a war hero is not a plus when running for President: Two words - John Kerry.  For that matter, Bob Dole was a war hero (he received two Purple Hearts and a Bronze star), as well as George Bush Sr. (He received the Distinguished Flying Cross due to his admittedly brave actions over Chimi Jima)

3.  The media glow is just starting to come off: A lot of people on here rightfully claim that Obama's head to head numbers can come down, but they don't realize the same thing is quite likely to be true about McCain.  McCain right now is in a position very similar to Rudy Giuliani six months ago - people generally like him (and he does fairly well in head to head matchups), but they don't know much of anything about him besides his maverick reputation.  One difference though is while people who didn't know Rudy assumed he was more conservative than he is, people who aren't paying attention assume McCain is more moderate than he is.  A disturbing amount of people have no idea that McCain is pro-life and a die-hard supporter of the Iraq war.  His positions will undoubtedly come under increased scrutiny as we get into the fall.  

4.  McCain is repeating the same themes that didn't work for Hillary: You know, the whole "speeches don't solve problems thing."  Given Obama does best with crossover independents and Republicans, my bet is swing voters are going to be even less amenable to this argument than those who have voted in the Democratic primaries and caucuses are.  

5.  The economy: McCain has nothing to say on the economy really.  He's made it clear he isn't particularly interested in economic issues, and when he does discuss them, he just spouts right-wing talking points about cutting taxes on businesses (which we've already done a ton of for the past seven years), and cutting back on social spending.  Given the U.S. is likely to be in full-fledged recession by the fall, this will be some thin gruel for swing voters.  

6.  The war: When two-thirds of Americans disapprove of Bush's handling of the Iraq war, half want a withdrawal within a year or less, and independents and Democrats hold essentially the same views on Iraq, it's impossible to see any advantage for McCain here.  The only reason why he's still somewhat credible with swing voters is a large number of them don't realize that he's for keeping U.S. troops in Iraq another hundred years.  This will change.  

7.  The eight-year itch: Generally speaking, one party doesn't hold the white house longer than eight consecutive years.  George Bush Sr. was an exception of course, but the rule is by this time fatigue sets in on whichever party controls the executive branch.  And lo and behold, Democrats do have a large generic lead now, and the attitudes of Americans on taxes, social spending, and foreign policy are becoming closer and closer to Democratic policy

8.  McCain is less likable than Obama: The candidate viewed as more likable always wins the presidential elections.  Obama can come across as cool at times, but he's a confident man with an important slice of self-deprecating humor at times.  McCain is an ugly old man who is well known for having a temper.  I think it's possible that McCain might be anointed as "likable" by some in the press, but I think that it will go over as well as Grandpa Fred once people get to know him.  

9.  McCain's campaign is far worse than Clinton or Obama: I don't think Clinton's campaign has been startlingly awful, just startlingly awful post super Tuesday.  However, it's important to remember McCain mostly won the primaries as a default candidate - everyone else running had major flaws and imploded in various ways, until he was the last man standing.  While his campaign probably did play a strong role in winning New Hampshire, it hasn't done much of anything else, and couldn't get out of the mire until Huckabee started to slay Romney.  He was also broke as of New Years.  I see nothing within his campaign which makes me think it's anywhere near the caliber of either Clinton's campaign or Obama's campaign.  

10.  The divided right: In recent history, there have been three losing Republican candidates: Ford in `76, George Bush Sr. in `92, and Bob Dole in '96.  In all cases, the right-wing base failed to embrace the Republican candidate - they didn't really see him as "one of their own" and there wasn't much enthusiasm to turning up and voting for any of them.  Of course, Bush won in 1988 despite the right-wing having huge misgivings about him, so there's a possibility that McCain could survive as a viable candidate even if the right never truly embraces him.  Still, the fact that Limbaugh and company have not closed ranks yet - and Huckabee continues to do fairly well in primaries, despite not being viable, speaks ominously about McCain's chances of healing his party.

Given all this, I'd say Obama, if he secures the nomination, has around a 70% chance of winning against McCain.  I actually think the general election will be far easier for him than the primaries have been.  Of course, this is all just my opinion, and I'd love to hear the opinions of you guys.