Unfortunately the Tea Party does not swing anybody. If anything, they turn off independents. As for Palin, she's the only VP candidate in living memory who managed to hurt the ticket. She delivered millions of votes to Obama. She also sank a lot of candidates down the ballot. Norm Coleman would have definitively survived without her. So Obamacare would never have happened without either Sarah Palin or Pat Toomey.
The Republican Party turned sharply right about 1990 (to the point where Reagan would have been expelled from the party as RINO now), while the country turned left. I'm afraid there will be no Republican president until at least 2025, and when we finally have one, he will run on the platform of dramatically increasing spending on the national health system (which we will have by that time).