You're correct, its got a fair mix, with potentially more conservatives than liberals (though at this current time of active posters I'd dare say its at the closest split we've had in some time).
HOWEVER, your question has nothing to do with the conservative bend on the forum, but specifically about parties people are affiliated with.
DP has a pretty decent cadre of Libertarians for one. Two, since 2006 there's been a number of people who are soundly conservative, who soundly vote republican, but no longer identify themselves with that party.
You are trying to postulate that somehow low numbers of people that identify as "Republicans" will hurt them at the voting box. I think this is a faulty and illogical assumptions based on little facts and a misreading of the evidence presented. For this to be the case all, or at least a large portion, of those conservatives who did not identify themselves as part of the Republican Party would need to either vote 3rd party, vote democrats, or not vote. I would dare say, from the history and statements of many of these posters, that in reality the majority of said people would still be voting for the Republican nominee in electoins. As such, just because they don't identify themselves with the Republican Party at this current moment does not mean it will cause any damage or noticable shift in the Republicans votes.
This becomes even more true when, by examining your previous posts, its patentedly obvious why you think the issue CURRENTLY is happening...IE the attacks on Health Care. However, the majority of those not identifying with the GOP started doing so long before the Health Care debate was truly raging. Indeed, I dare say I don't know of a single, solitary, person on this forum that listed themselves as a Republican who has changed their party identification due to Health Care.
On the contrary, the majority of those that now don't claim to be part of the Republican Party did so back in 2006 due to anger at the fiscal irresponsability and failure to uphold the principles of conservatism by many in office, or in 2008 when a moderate republican who made a career the past 8 years of insulting conservatives and screwing over those in his ideology became the parties choice for President. In both those cases, the complaint that caused the migration was NOT that they were unhappy with conservatism but really just the opposite, that they were unhappy with the lack of well rounded conservatism. To then turn around and insinuate and assume that somehow Republicans actually sticking to their principles for once, less government intervention in our private lives and increase in the size and scope of government, is preposterous.
So no, I fully reject you're hypothesis for the reason above, along with the fact that people tend to more readily identify with the party that fits their lean when that party is in power, on top of the fact you actually acknowledged in that this is a sampling of a few dozen people on a debate site which in and of itself means people generally more interested in politics than the average person. I don't believe the lack of people self identifying as "republicans" is going to hurt the GOP at the ballot box, and dare say that the acts of the majority of reasonable republicans currently in fighting against the auto-buyouts, fighting government ran health care, fighting any increases in taxes, fighting cap and trade, etc may end up actually helping them comparitive to 2006 and 2008. While the idiotic attacks from a vocal minority are just that, idiotic, I do not foresee any reason why they should be any more damaging than those same attacks that implied that the Bush White House knew about and purposefully allowed 9/11 to happen or that the government was peeking completely unchecked at every American whenever and however they wanted...let alone all the childish "dumbo" like attacks... and other such absurd notions that came out over 8 years.