There is much written on the 2008 Presidential Election, although the amount here is surprisingly small (as of yet). Many of the candidates are covered above, but one thing hasn't been discussed above, a facet that is very important: the fact that the 2008 Presidential election will hardly take place in a vacuum, but will be a nationwide election for all of the Representatives, one-third of The Senate, 11 state houses, and many many local elections, from mayor down to the proverbial dog catcher.
For the many foreign readers of this site, and many US readers who might be unclear on the matter, the President doesn't have some of the powers attributed to him. One of the largest powers of the presidency is actually the bully pulpit, the fact that the presidency carries enough respect around it that when he makes a statement, people are inclined to believe him,until he has throughly proved himself a liar. For example, the drive to war, even though engineered by George Bush and Dick Cheney, worked because they had control of the Senate and House, and the ability to convince or cow some democrats in both to go along with the war. Of course, by the 2006 General Election voters, seemingly upset over the Iraq War, or perhaps just showing fickleness to the party in power, voted a majority of democrats into the house, and, by a small margin, the senate. While the 2008 congressional elections might show some surprises, there is a good chance that the democratic margin might grow, perhaps substantially.
This means that if John McCain does win the presidency, he will be working against a stiff headwind. Any legislation he introduces has a good chance of being vetoed, and in some cases, there may be a large enough margin of democrats and liberal republicans to override his veto on some matters. Democrats in the house and senate can make the months of confirmation hearings that follow his inauguration quite difficult, choosing to grill his Secretary of Transportation on how they can run the nation's transportation ticket when they got that speeding ticket back in 1983. And, if they want to get really nasty, they can form special committees to investigate any scandals that might be buried somewhere. McCain is, I assume, well aware of this, and wants to avoid it.
One of McCain's pledges so far has been to keep the race about issues and ideas, rather than character politics. With perhaps some optimism, I think there is a genuine desire to avoid a scorched earth campaign, but I also think McCain is smart enough to know that if he pulls out the stops, and runs a campaign of FUD against Obama, playing the Jeremiah Wright video and starting to let people talk about "Barrack Hussein Obama", that it will be a Pyrrhic victory for him. This will stir up the type of hatred from the senate and house that will lead to the type of opposition outlined above.
In addition, McCain and his supporters are probably thinking of the long term prospects of their party. One of the basic strategies of the republican party was the Southern Strategy, to keep rural, conservative voters (in the south and elsewhere) in their column, and then to win elections by swinging a few key states. I've written elsewhere about the philosophical ramifications of this, as well as how it backfired in one case. But for a more immediate look, it might be interesting to look at a map put together by my friend Qousqous, showing the party affiliations of congressional districts:
http://farm3.static.flickr.com/2080/2268459714_1143cea08e_b.jpg
While one of the things this map does is show that most of the
conventional wisdom about
Red States isn't true, it is true in many of the
Blue States. The Republican party is down to one seat from
New England, and its distribution across urban areas of the West Coast, Central Atlantic and Upper Midwest also look tenuous. In some ways, I think this is identity politics in reverse: many suburban voters who might consider themselves moderates now associate the republican party, (however unfairly), with some of the worst stereotypes of rednecks. This might have caused long term damage to the party, and as more and more Americans grow up in a more pluralistic society, last ditch efforts to appeal to people's fears of those who are different might prove totally suicidal.
This presidential election, perhaps much more than most presidential elections, is about more than just who gets to fulfill their ambition for a position of prestige. It is also about congressional elections, the future of parties, and the future of the country. For those reasons, I think that McCain will have to run a safe, polite race against Obama, even if it means defeat. If he chooses to attack Obama in an underhanded manner, it would make his term next to impossible, and put the Republican Party in a position that it might take ten years or more to recover from.