Now that Romney has all but wrapped up the Republican nomination I want to try and get out in front of the what are inevitable questions about whether anyone else will enter the race to try and capitalize on the dissatisfaction with Romney and Obama. In short, even if someone does it probably won't matter.
In the unlikely instance where we have another Bush v. Gore it could matter that someone like Gary Johnson or Ralph Nader gets 1% of the popular vote. But even then the race within states, where it actually matters, it would have to extremely close between Romney and Obama. I guess it's conceivable that some states could end up this close. In order for that to happen I think the economy would need to continue to grow slowly and for conservatives to not rally around Romney. I can see both of those things happening to some extent.
But the key point I wanted to make is that I think most conservatives will rally around Romney. To what extent they rally (turnout) will be important. But there aren't enough conservatives who will outright reject Romney for their vote for a third party candidate to matter too much. The worst they will do is not vote at all. The same goes for dissatisfied liberals. Liberals who voted for Obama in 08 will not all of the sudden jump ship in waves to support a third party candidate. But they could just stay home.
The reason I believe this is because most people have fairly well defined partisan identities. You'll inevitably hear about all those independents that make up such a huge % of the population. Well, the reality is that most of those self-identified independents vote in just a partisan a manner as self-identified liberals and conservatives. Only about 10% of them actually change their vote between parties on a consistent basis. So while I'm sure Romney and Obama will devote some energy to getting some people who are on the fence, I think most of their effort will be geared towards getting their supporters to show up.
That's why I've been so critical of many of Obama's legislative and PR strategies throughout his first term. I don't think he has done enough to keep his liberal base happy and thus willing to vote for him in the same numbers as they did in 08. As for Romney, he's probably happy Santorum is out because he needs time to get the conservative base on board. He's probably also hoping that the economy only grows very slowly from now until November because regardless of how successful he is at getting conservatives to turn out, that will probably be the most important factor.