In my opinion, even if the GOP made an announcement tomorrow that they embraced gay marriage, legal pot, atheism, and the social welfare state, I'm still not convinced they'd have better than the short end of a 60/40 shot at the Presidency. I think the Left knows the Republicans can never win the Presidency again...but needs to convince them they _can_, to lure them away from their base of beliefs so that they will lose their advantage in midterms.
If Republicans stick to their beliefs, never win the Presidency again, but keep control of congress away from Democrats via dominating midterms, that stalls the democrat agenda pretty effectively (witness the last 4 years of Obama's term). But if the Republicans abandon their beliefs to try to win back the White House, they probably lose the Presidency anyway, plus the Congress also, and we get one-party democrat rule.
That's why people on the Left have to convince the Republicans to change their beliefs. Republicans sticking to their guns, even if they only represent 30% of the public, keeps the football away from the Democrats. As a fairly right-wingish person, I personally have no problem with the Republicans never winning the White House again. I say, let the Democrats run it and take the blame, while we keep the purse strings out of their hands during midterms. The main task is convincing Republican voters that the White House is lost. The Left is the one who needs to convince them to still believe.
The problem isn't Republican beliefs, it's the delivery of them. You can have the greatest ideas in the world, but if Pee Wee Herman is your pitchman, good look at people taking you seriously. Their constant fail is assigning blame to a huge swath of potential voters. Why would someone vote for them if they think the party dislikes them? Who was the idiot that said something about "black people on welfare?" It was as if ONLY black people are on welfare in his world, totally disregarding the various colors that are in that system. How do you think that plays out to black guy not on welfare? Why not simply say "people on welfare" than using one specific group. That would have played out infinitely better.