The House can prevent Obama from doing anything too terrible.  As for the blaming Republicans for gridlock, Democrats will blame Republicans for gridlock no matter what happens. 2008 showed us what happens when we strategize based on what we think the Democrats will say about us.

Also, the good candidates waiting in the wings (such as Rubio and Pence) will have their presidential hopes delayed and potentially destroyed by a Romney presidency. 

My problem with Romney on SCOTUS is that I think he is far more likely to appoint a David Souter or John Paul Stevens than a Scalia or Thomas.

According to exit polls, 22% of conservatives refused to vote for John McCain. This is a higher percentage than refused to vote for a Republican candidate in a two way race since the '80s.

RE: Frozen Chosen Part 3 of 3:

 “John Mccain - not exactly a conservative's dream - had no problem firing up the base in 2008 when it came to voting.  He received a higher number of conservative votes than any previous GOP candidate so the whole "firing up the base" meme is a real canard.”

McCain only received a higher number because more people voted in 2008 than voted in the previous elections.  Going by percentage McCain only garnered 78% of conservative votes.  By comparison, George W. Bush won 84% of conservatives in 2004 and 81% in 2000.  That means more conservatives voted AGAINST McCain than any previous GOP candidate in a two way race.  The only Republican candidates since the '80s who received a lower percentage of the conservative vote than McCain had third party challengers who ate up conservative votes.

Part 2 of 3 of my response to Frozen Chosen:

“Comparing independent vote totals from 2008 to 2010 is truly comparing apples to oranges as the circumstances of those elections were completely different.”

You're right - the circumstances were different.  In 2008, Republicans nominated a moderate and he failed to garner Independent support.  In 2010, with Barack Obama in the White House, the Republicans ran far more conservative candidates and earned more Independent votes.  Look to my example in Florida.  With Barack Obama in the White House and the election boiling down to Obama’s policies vs. the Republican alternative, Independent voters in a crucial swing state overwhelmingly chose a conservative Republican over a moderate Republican.  If all a liberal Republican needed to win Independent support is a liberal president to campaign against, Charlie Crist would be a Senator.

Frozen Chosen -
Anon made excellent points, to which I add the following:

“When polls showed Mccain leading Obama by 12 pts in January 2008 Obama was a candidate and not the president.  Romney's 6% lead over President Obama is much more significant than leading candidate Obama.”

In my post, I also give the example of President Bush losing by 7 points to John Kerry in early 2004. Those early polls were not a good indicator of the final result and there's no reason to believe early polls will bear any resemblance to the final result this time.

Close only counts in horseshoes and hand grenades. Kerry couldn't beat an unpopular incumbent who had the media campaigning against him. Also, relying on the base holding their nose certainly didn't work for John McCain.

To answer your first question, the difference is that Romney isn't the only thing standing between John McCain and the nomination. The conservative support for Romney in 2008 was largely a last ditch effort to prevent McCain from winning once Giuliani, Thompson and Huckabee fell by the wayside.

1. The early polls showing Romney leading Obama are meaningless. 

2. Romney has been campaigning for a year and still has failed to earn the support of 75% of his own party. 

3. I never argue that Romney is hopeless.  Rather, I think his electability is not guaranteed and he has serious problems that need to be considered before he's dubbed the electable candidate.

In 2004, the Democrats thought the same thing about George W. Bush.

 The problem I see with both Gingrich and Romney is that both don't seem to be anti-big government. Romney's "Keep the good and throw out the bad" approach to Obamacare and Gingrich's support of the individual mandate seem to point to a progressive approach that says "I want to be president so I can make big government more efficient." 

Well, she did make Wycleaf Jean want to speak Spanish in that one song.  Maybe she'll inspire this generation to study. 

 I think that's what may happening with Herman Cain.  It seemed as though many conservatives voted for him this weekend because Perry was underwhelming. 

As for Christie, he's a RINO if he comes from any state more conservative than New Jersey.  I think if he runs, he'll burn out faster than Thompson did.