…this is the best opinion piece I’ve read on the subject.  Short, simple, and to the point:

WHAT JOHN MCCAIN UNDERESTIMATES

1. The astonishing enthusiasm that Obama inspires in his supporters — and how much it contrasts with the respect, but not passion, McCain enjoys from his own backers. (And the size of Obama’s crowds…)

2. The “Major League vs Little League” difference between Obama’s infrastructure and his own.

3. The inherent difficulty/sensitivity of running against two figures at once. McCain will have to 1) explicitly criticize a sitting Republican president before Republican audiences and 2) prevent the historic event of electing the nation’s first African-American president that many in the country (and the media) desire.

4. The ever-present danger on the trail that he might evoke Bob Dole with a Bob Dole-like misstep (fall off a stage, sound like a Washington fossil, seem angry and out of touch).

5. How little most Americans care about foreign policy (beyond the Iraq War) when the economy is in the tank.

6. How many voters (even Republican stalwarts) dread the idea of a virtual third Bush term.

7. How many members of the media dread the idea of covering a virtual third Bush term (and how much they buy Obama’s argument that McCain is an extension of Bush-Cheney).

8. The extent to which McCain’s lack of an economic message could make Obama (who also is challenged in adequately addressing the economy) seem like Bob Rubin, Bill Clinton, and Lou Dobbs all rolled into one.

9. That many of his party’s wiseguys and wisegals see polling data suggesting his chances of winning are no more than 30% (and how much it infects their cable TV appearances).

10. That in modern America, perception is often reality and style often beats substance.

11. That age is only a number unless it’s a really high number — then it’s a liability.

12. How old he looks when he is acting “presidential” on the stump – and how incongruous it makes his message of change appear.

13. How powerful debates might be when the allegedly inexperienced Obama of allegedly questionable judgment goes toe-to-toe with McCain, even on national security, and is therefore deemed of sufficient strength and stature to be president by many.

14. How valuable Obama makes voters feel (”we are the change we have been waiting for”) – while McCain’s campaign instructs and lectures voters.

15. How forcefully Obama will now move to the center as a mainstream, optimistic candidate celebrating both change and America’s greatness.