It's social issues. People, especially moderates, think Republicans are too extreme on social issues (abortion, gun rights, gay marriage, etc.). I don't think Republicans need to move to the left/center to win the presidency, though, they just need to downplay social issues and focus more on economic issues, like taxes and spending. The Conservative Party in Canada has done this with pretty good success, so the GOP should try it, too.
The Canadian's Conservative Party governs to the left of the US's Democratic Party.
As you might consider it, "A bunch of commie(s) govern Canada".
