I don't think the moderates have control of the party right now. The emotion is all with the Tea Party branch. I don't see them being willing to compromise. But I'm not sure what the compromise would be. It's a battle between gaining control of the Senate and purifying the party. Those two goals aren't often compatible. I'm sure that almost every moderate would vote for a Tea Party candidate in both the primary and general election if that candidate was the most electable GOP candidate in the state. And they would vote for that candidate in the general election if he or she won the primary. The Tea Party would only vote for their candidate in the primary, whether or not he or she had a better chance in the general than a more moderate candidate would. And they might just stay home if the moderate GOP candidate won the primary.
Cheer me up by convincing me that I'm wrong. 
Moderates control the party; there is not one of the new tea partiers who holds any real senior position of power in the GOP hierarchy. Tea partiers/conservatives are the very flashy tail on the dog, but the dog still wags the tail, not the other way around. As a moderate you should take some comfort from that.
I think also it would help if we avoided as much hyperbole and rhetoric as possible. It's not really helpful, although it's tempting, to say tea partiers want to "purify" the party; they want to push the party's political principles and goals in a much different direction than they are now and that necessarily means challenging those who set, and who maintain, those current policies.
What makes a particular candidate "electable" is a very complicated analysis I would think. For one thing, it depends on whether or not people turn out in the primaries to vote for a given candidate. Almost by definition, if a candidate cannot get enough votes in the primary, he or she is unlikely to get enough votes in the actual election. It also has a very large subjective component to it. For example, many people would consider their favorite candidate to be the most electable because he/she is their favorite candidate.
"Electability" also contains a contradiction: being "electable" in a party primary is not the same thing as being "electable" in the general election, but the candidate for the general election is the one chosen in the primary and therefore is always the one who was the most "electable" in that primary. This contradiction pops up all the time on both sides of the political divide.
Sorry for taking this in little out-of-order snippets. If I knew how to achieve the compromise, then I'd be the frontrunner for presidential candidate right about now. However, one approach that the moderates could take is to basically peel away a significant number of a tea party candidate's supporters by appealing to them directly in a way that doesn't put their beliefs and goals down, but that tries to put them into a broader context and, precisely, tries to convince them that having an 'R' win the election right now is more important than that the winning 'R' satisfy every last single desire of the voters.
This, for one thing, requires a lot of listening. I would suggest that moderates, or at least their more senior staff, get down to the hyperlocal level and start talking to self-identified tea partiers, find out what their actual motivations are, find out if they're just lashing out in anger and simply fastening on to the one person who seems to be really listening to them, or if they have some dogmatic or ideological predisposition that won't be easily changed by persuasive argument.
Have those mythical kitchen-table discussions with as many people as possible. From there, try to distill what they've been saying into something simple, sort of a verbal set of bullet points, like "ok, I'm hearing that you're worried about ___________ and ___________" so that you show that you've actually engaged with what they're saying, and then explain - in plain English - why your policies are more likely to lead to some of those goals being satisfied than are others' policies. And for that, don't lead with the electability argument - if you do people will just think you're calling them stupid and they'll turn off. Also try to explain, in apologetic terms, why some of their goals are simply unattainable, or are partly unattainable. For example, abortion will never be illegal in this country - as much as that's a bitter pill for many to swallow - and that should be explained in careful, measured tones, without blaming anyone for being evil or full of hate or engaged in a conspiracy, or stupid, or ..., and then followed up, where possible, with alternatives, such as focusing on getting rid of government funding for abortion, which can itself be placed in a larger philosophical context, one that is not religiously driven, such as that abortion is such a private, personal matter that the government has no business getting involved with promoting or preventing abortion because that is a matter of respecting each individual's Constitutional rights to freedom and liberty. Emphasize that the rights to freedom and liberty aren't limited to just the smart or the wise, they're available to everyone, no matter how smart, wise, or stupid.
I could go on and on, but I'm tired and need to go to bed.
