voters will punish these guys for being too conservative (Jim Young/Reuters)
You don't want these candidates moving so Right in the Republican primary that it becomes impossible for them to win the general election, because it will become a self-defeating message in the primary.
People want to win. They don't want somebody who goes so far to the extremes of either party that they lack a chance to carry a victory off in November.
If today's GOP were a sane party, Rove's comment might make sense, but today's GOP is anything but sane. Everything we've seen over the past couple of years is that nothing is too right wing for the GOP. Even Mitt Romney, despite his past, is now running as a born-again teabagger, at least in substance if not in spirit. Not a single one of them said they'd agree to a deficit reduction deal with a 10-to-1 ratio between spending cuts and tax hikes.
The only really big domestic policy difference among the candidates during last Thursday's debate came when Jon Huntsman said he favored civil unions and that he supported Boehner's debt deal. Other than that, watching the debate was like watching a bunch of inbred red staters throw wingnut confetti on each other.
With the occasional exception of Jon Huntsman (and Ron Paul on foreign policy), all of the GOP candidates are already very far to the right, at least in terms of what they say they believe in. Tim Pawlenty just abandoned his campaign because conservative activists didn't really believe he was one of them. Mitt Romney can't break out of the 20 percent range because conservative GOP primary voters don't believe anything he says. Meanwhile, not a single candidate has got in trouble on anything by moving too far to the right...because no matter what Karl Rove may say or believe, in today's Republican Party, there's no such thing as too far to the right.