I know that Obama's successes or failures will play a role in what candidates the GOP will field in future elections, but, for the moment, let's set Obama aside and focus on what has and could happen to the Republican party.

Back in the 60s, Barry Goldwater saw an opportunity and a danger in recruiting the social conservatives to the GOP (and shift the nature of political parties from a regional one to an ideological one).  Goldwater wanted to get the votes of all of the rightwing conservatives, but did not want to allow the extremists to come to salient positions within the party.  Birchers, KKK members, radical Christian fundamentalists, and other extremists were marginalized within the party, but, as Goldwater suspected, they wouldn't have any other party to vote for as the Democrats were leading the charge on pursuing civil rights laws and enforcement.

For a time, Goldwater's plans worked.  However, the radical fringe started to percolate up in the GOP during the 80s, increased the grip on the party in the 90s, and became near total control in the last decade.  The few remaining moderates have fled the party, or are near pariahs to the base (example, Sen. Collins of Maine, despite the fact that she almost always votes with the GOP).

Is the modern GOP the twisted misanthropic party that Barry Goldwater feared?  And where do they go from here?

Sarah Palin appears to have a lot of support from the base of the Republican party.  Will the braintrusts of the GOP allow her to take the nomination?  Will Michael Steele allow the "pieces on the chessboard" to move that way?  Or is there even enough organization within the party at this point to prevent Palin from taking the nomination if she goes after it?

Or, if Palin is prevented from taking the GOP nomination, will she try to run as a third party candidate?  I, for one, would love this.  It could have an inverted effect of the 1912 election.  For those not familiar with this election, it was the only election in U.S. history were a third party received more votes than one of the two major parties.  The GOP candidate was sitting president Taft, the Democrat was Woodrow Wilson, and the third party candidate was former president Theodore Roosevelt, who, dissatisfied with the way Taft was running the country, decided to run in the "Bull Moose Progressive" party for president.  Roosevelt was quite popular, and Taft decided to not even bother campaigning anymore when he found out his former boss was entering the campaign.  Here's the history that normally isn't emphasized:  The liberal and moderate Republicans who supported Roosevelt (more of regional party than an ideological one at this point) were effectively castigated from the party.  This would have a very profound effect on the GOP leadership in the decades to come; all were hard right ideologically.

Could the inverse happen if Palin runs on a third party platform?  Could the radical fringe all support her and her new party, and leave the few remaining moderates in charge of the GOP?  Of course, splitting the vote in a party *always* leads to the other party winning, but, it could lay the groundwork for a more reasonable GOP emerging in the future (sans social conservatives).

On a side note, I have a suggestion for the Palin's third party name if she decides to go that route:
"Dead Moose Regressive Party."