I have heard some people argue in favor of voting for Romney as follows:
1) Romney and Obama are not that strikingly different. Both are moderates, Obama is a shade more liberal, Romney is a shade more conservative. In general, I agree with this point, in part because Romney, who during the primary claimed to be a far right zealous Republican, has during the general election, totally flip-flopped and claimed to be a moderate.
2) But the GOP has refused to compromise one bit, insisting on portraying Obama as a radical, making getting rid of him their "#1 job", etc. etc. In general, I think this statement is also true.
3) Conclusion, as long as the GOP has the house (and it looks like they will retain a majority their, even if they lose a couple of seats), that it's best to have Romney as President in order to get things done.
But I don't agree with their conclusion.
For the purpose of this argument, let's assume that both assumptions (#1 and #2) are correct - the candidates are close and the GOP has actively refused to compromise (in reality, the DNC is also partially to blame - although much less so) . Because if the blame resides on the Democrats as well as the Republicans, then their pro-Romney argument falls apart as the Democrats will be just as annoying and refusing to compromise (and via their Senate majority, just as much a roadblock).
There are several reasons to not bow down to their extortion.
1) Those 'shades' they mentioned in step 1, are important. Government/legal progress is made by baby steps more often than by large steps. (This is Legal change as opposed to Political change - political change tends to happen in large steps.) It's the difference between accepting gays in the military and maintaining 'separate but equal'. It's the difference between getting another more conservative Supreme Court Judge that might be a Roberts (or might be a Scalia) and getting an actual liberal on the Court.
2) We don't give in to extortion. If you do, you invite more extortion. Better to get nothing done and train the the extortionist not to extort then it is to bow down to them and accept their demands. We are free men, not slaves, and the price of freedom is sometimes high. If this means we go through some pain now, then we gain far more in the future by having better leaders that have learned from their mistakes.
3) You can't trust an extortionist. They won't pass reasonable laws even with Romney in charge. That is, first they demand X, when they get it, they then demand 2X. Better to have nothing done than to have bad things done.
4) If the other party is in fact being that much of an extortionist, it opens up more objectionable actions by the president. That is, the GOP is not the only one that can act unilaterally. The president can and will do a lot without their help, particularly if they refuse to act. A key example of this is the president's ruling on immigration. When the GOP refused to act on immigration reform, he declared we won't enforce the law against certain people that are clearly not criminals. (If your parents bring you hear when you are a minor, you have not broken the law, your parents have.) This frees the executive branch to devote precious and limited resources to pursuing actual, dangerous criminals.
If the GOP never realizes that the Democrats can fight back, that just means the President will have an easier time defeating them. If they do, they will stop trying to extort us and start compromising.
For these four reasons, it is a bad idea to vote for Romney if your only concern is to get things done.
As a side note, much of our political structure is designed to prevent things from getting done. That is one of the reasons we have both a Senate and a House. So a stalemate is not quite as bad as people think it is.