It doesn't matter who the Republicans run, they will lose. Look, the electorate is still pretty much split, but any Democratic candidate has a huge advantage. Despite the fact that Republicans have the advantage in House races, the fact remains that for the last few elections, Democrats have taken more votes in House races than Republicans. The votes are just in the wrong places to give Dems the House, but when it comes to the presidential election, Dems have a huge advantage. The second problem Republicans will be facing is the fact that the economy is on the rebound and gaining strength little by little. By election time, the economy is going to be looking good. Bottom line is that the Dems could run Howdy Doodie and win in 2016.
The actual election record is that when the GOP nominates a real conservative, they win. When they nominate a moderate that is supposed to have a better chance to win, they lose. Why? Because the GOP is like 80% conservative. The electorate is about 20% liberal, 35% moderate, and 45% conservative (as self identified). Yet in elections where Republicans lose the exit polls show about as many conservatives voted as liberals and the moderates are 40% of the vote. Why? Because moderates FAIL to get all the conservatives out to vote. The GOP RINOs claim that the conservatives have no where else to go but to vote for them, and they are proven wrong every election that has a moderate run for the GOP. Where do the conservative voters go? To the couch and stay home and do not vote and that means the GOP loses.
IF the GOP nominates a conservative, the GOP wins, every time, and it will be the same in 2016 as well.