I would like to take a moment to address something that you hear every Presidential cycle and which is making the rounds again in force this year - the threat that "if [Candidate X] wins the nomination, I am going to stay home/vote third party/vote for Obama." The loudest and most vocal group of these folks during this election cycle are the Romney opponents; however, I've heard a lot of libertarian conservatives make the same threat about a potential Santorum nomination, and a lot of folks bothered by Newt's serial adultery who have made the same threat if Newt gets the nomination.
Let me start out by stating the obvious - there is no one who is going to force anyone to vote and each person is certainly entitled to make their own choice about whether they will take time out of their day once every other year to go to the voting booth and cast a ballot - a point which applies a fortiori when it comes to the decision whether to donate to/volunteer for a candidate. If a person simply feels that they can't pull the lever for Romney/Santorum/Newt, then I respect that decision even if I disagree with it. After all, I myself would have been unable to pull the lever for Rudy in 2008 because I have moral qualms against voting for candidates who are in favor of legalized mass infanticide.
The problem I have is with the folks who believe that their statement of refusal to vote for the Republican nominee presents some sort of existential threat to the Republican party that the party should heed and pay some sort of special deference to. The entire mentality that says, "If you, the Establishment, foist Mitt Romney upon us, then we are going to show you good - we are going to start a third party and destroy the Republican party forever!" A few points are in order about this line of thinking.
First, the Republican party nomination will be won not by the "Establishment" but rather by Republican primary voters. If indeed Mitt Romney wins the nomination, it will be because more Republicans voted for him than for any other Republican candidate. In light of this undisputable fact, I am at a loss as to what the folks who are currently threatening third party votes/voting for Obama/staying home are hoping the Republican Party will do in the event that the Party is inclined to cave to their threats. Do they want the Republican Party to disregard the will of Republican voters and nominate someone who didn't get as many votes as Mitt Romney? Such a solution is absurd on its face but that seems to be what many people are asking for (even though they aren't taking their reasoning this far, which is its only logical endpoint). If you are really and truly angry about the prospect of a Mitt Romney nomination, may I suggest that you spend more time convincing your fellow voters to vote for someone else rather than screaming impotently at people who cannot fix your problem for you. And may I also suggest that "If your guy wins the nomination, I am taking my ball and going home" is not that persuasive of an argument to the average GOP primary voter.
Second, this argument vastly overstates the importance of the person who is making it in the grand scheme of political history. Every potential nominee and actual nominee who has ever been nominated has been unacceptable to some subset of Republican voters. That fact notwithstanding, we've had a pretty decent run in terms of winning the White House since the end of the FDR administration. The polling right now would clearly suggest that Romney has the best chance to beat Obama head to head even given the allegedly enormous number of people who would sit out/vote Obama if he is the nominee (unless we assume that huge numbers of people are lying to pollsters about their willingness to vote for Romney in the general right now). The folks who are caterwauling right now ought to really stop and consider the implications of this fact. If, in fact, there is a nebulous Republican "Establishment" that is somehow able to control the primary process and override the will of Republican voters (something which I contend is ludicrous but is nonetheless fervently believed by many people, apparently), then the worst thing that could possibly happen to the conservative movement would be for them to get the idea - supported by the evidence - that Republican nominees could win without any support at all from movement conservatives. And if movement conservatives loudly sit out and/or vote Third Party and Romney wins anyway, that is exactly the message that will be sent.
But moreover, there is a normative aspect of this that is at work here which I am dismayed to see so many alleged conservatives disregarding. Being elected to the Presidency in a country of this size requires a massive team organization effort that frankly cannot be accomplished outside of the current two-party framework. Despite the earnest protestations of various assorted cranks who have risen up throughout the years, a vote for something other than a Democrat or a Republican in the Presidential election is a completely wasted vote. The Democrats show no inclination to discontinue their parade of socialist freakshow nominees any time in the near future, so it is facially obvious that any person of even nominally conservative beliefs will generally find the Republicans' nominee to be the better choice.
The Republican party is composed of millions of different people with widely divergent beliefs and priorities. In different regions of the country and different Congressional districts, very different kinds of Republicans stand the best chance of being elected. When it comes to the country at large, we have a democratic process which determines who we as a party will put up for the position of President. This person will be the only meaningful alternative to the thinly veiled socialism of the Democrats that the public can choose. Sometimes, as a Republican, your choice for nominee will win, and sometimes your choice will lose. When the process is said and done, as a Republican, only a truly unusual set of circumstances should prevent us from being able to lay down the arms we have turned against each other and working together to defeat the Democrats and their twisted vision for America.
Again, if someone can't bring themselves to vote in November under their own conscience, that is their own business and I will not judge them. But the wailing cry of "I'm taking my ball and going home if I don't get my way!" is something our parents hopefully taught us was wrong about the time we turned six years old. I see no reason why it should be treated with any more seriousness than we would treat a wayward six year old, even if it were possible to do so without thwarting the democratically-expressed wishes of the GOP electorate.