The conventional political wisdom is that presidential candidates run to their base during the primaries and then back to the center during the general election. Usually there is an unspoken agreement not to give each other serious grief over the things said to win the primaries, because both candidates have said equally embarrassing things.
2004 was an anomalous election in this sense, because both the Bush and Kerry campaigns sensed that there was not very much center up for grabs. The normal 12-14% of undecided moderate voters in the center without strong party identification had shrunk that year to less than 6%, which left both the Dems and the GOPers in the weird position of having a better potential for picking up votes in their respective bases. There were more anti-abortion, social conservatives, and evangelical Christians available to vote for Bush, and more environmentalists, gay rights advocates, and anti-war activists available to vote for Kerry that undecideds in the middle.
As a result, both Bush and Kerry ran to their bases to win their nominations, and then ran even further toward their bases during the general election campaign. This produced the unusual situation of Bush running hard right while Kerry ran hard left.
This year something even stranger is occurring. Senator Barack Obama is very obviously pursuing the traditional strategy of running back to the center, earning him fire from his liberal base that somehow expected he wouldn't do it.
Senator John McCain, on the other hand, actually won his nomination by more or less ignoring his base, running toward the center during the primaries, completely alienating the hardline conservatives quite early in the process. Now he's spiraling around trying to find a direction.
Meanwhile, Bob Barr--having pissed off whatever base he had in the Libertarian Party--is clearly running for the libertarian-leaning Republicans, most of whom would normally have been considered part of the GOP base.
And all the latest polling reports suggest that he's eating into that GOP base.
What makes this really interesting, however, is the potential dynamic for John McCain (if he's smart enough to take advantage of it).
Make one assumption for the sake of argument: Iraq could be off the table as a major issue by October. The fact of the matter is that American voters have short memories. If the current, apparently positive trend in Iraq holds up, and we are drawing down troops and declaring victory, Senator Obama will lose one of his key issues. He will thus be thrown back on domestic issues.
His stances there got a pass in the primaries, but since McCain never went seriously after his own base back then, he's now free to go after Obama as too socially, big-government liberal to be trusted as president. He'll have to do it hard, because Barr will have infiltrated the GOP base.
This could get really interesting.