Richard Nixon famously said that Republican presidential candidates should run to the right in the primaries, then to the center in the general election. But what happens if they tilt so far rightward that they wind up ceding the center?

The current crop of candidates is risking that result. President Obama may be highly vulnerable in 2012, but if Rick Perry and his rivals don't clamp down on the crazy talk, they may well blow it.

Sensible Republicans realize this all too well. Mark McKinnon, an ex-George W. Bush strategist, spoke for many the other day when he contended that Perry and company "seem intent on putting an increasingly ideologically conservative and intolerant face on the party. They are pulling the primary contest so far right, the party will be far less attractive to the independent voters needed to win the general election."

Independents backed Obama by 8 percentage points in 2008, but they're currently sour on the president; in the latest Gallup poll, only 36 percent gave him a thumbs-up on job performance. It would appear that these centrist voters are ripe for the taking.

But this is no way to win them over:

Declaring that evolution is "just a theory that's out there."

Insisting that the scientific consensus on climate change is "all one contrived phony mess that is falling apart under its own weight."

Decreeing that revenue increases of any kind are unacceptable under any and all circumstances, and signing a pledge to that effect.

Promising to fill all key cabinet and executive jobs with foes of abortion, and signing a pledge to that effect.

Asserting that "it's time for us to just hand [America] over to God and say, 'God, you're going to have to fix this.' "

Announcing in a book that Social Security and Medicare are unconstitutional and should be scrapped.

Contending that gay Americans are "part of Satan."

Dissing the Bush-appointed Federal Reserve chairman as "treasonous."

Insinuating (yet again) that Obama is insufficiently American and insufficiently in love with America.

Perry dominates that small sampling. What's noteworthy is that the more he talks, the higher he climbs in the party rankings. Gallup said Wednesday that he had vaulted past Mitt Romney into first place as the preferred nominee, and that speaks volumes about the heavily rightward tilt of the post-Reagan Republican electorate. Reagan himself would be dismissed these days as way too moderate; he'd be down in the polls with Jon Huntsman, whose sane rebuttals of Perry have earned him 1 percent support.

In fact, let's talk about Reagan. Many conservatives today scoff at the notion that the current candidates are too extreme to beat Obama. They point out that Reagan was widely reviled in 1980 as too conservative and therefore unelectable. Many in the media made that case. So did moderate Republican John Anderson, who ran that autumn as an independent; as he argued in March of that year, "I am afraid that the nomination of Mr. Reagan will only ensure the reelection of [Jimmy] Carter and further ensure the continuing economic disaster that we have suffered now for three years."

But here's the flaw in the current conservative argument: Reagan in 1980 did not talk like an extremist, in the mold of Perry or Michele Bachmann. He had no interest in doubling down on crazy.

Reagan didn't equate gay people with Satan, or talk about them much at all; two years earlier, he had even opposed an antigay California referendum. Reagan didn't sign any pledges about abortion; he rarely even mentioned abortion. Reagan didn't sign any pledges never to hike taxes; indeed, as governor, he had repeatedly raised taxes. Reagan didn't question Carter's patriotism. Reagan didn't declare that he wanted to do away with Social Security and Medicare. Quite the contrary, he publicly (and falsely) denied during the campaign that he had ever opposed the concept of Medicare.

By contrast, the new Republican front-runner is openly adamant about whacking those federal safety nets out of existence. No wonder McKinnon and many of his party establishment friends are so nervous; it would be fascinating to watch Perry, during the autumn '12 campaign, tout his stance on Social Security and Medicare to audiences in senior-heavy swing states such as Florida and Pennsylvania. I also wonder whether his faith talk, his public willingness to name God as his Mr. Fix-It, would go down well in swing suburban enclaves - say, Bucks County, where independents typically prefer their fixers composed of bodily flesh.

Swing-voting independents would also typically prefer to trim the budget deficit through a combination of revenue increases and spending cuts. Yet, in obeisance to current conservative orthodoxy, all eight candidates on stage during an Aug. 4 debate declared (via the raising of hands) that it would be anathema to sign even a deal that contained $10 of cuts for every $1 of increases. This at a time when the polls show that independents want compromise, not ideological rigidity. Mindful of that sentiment, Jeb Bush, the ex-president's brother, told Fox News the other day that the candidates should say yes to revenue increases in the interest of finding common ground.

Fearful of ceding center turf, some Republicans are still clamoring for yet another candidate - some perfect someone who can presumably unite conservatives and moderates. The problem is that they all seem perfect until they take the plunge, at which point the litmus-testers tear them apart. Gov. Christie continues to tantalize Republicans, but rest assured that, somewhere in his record, he has said nice things about science. Strike one. He has already appointed a Muslim American judge and assailed the Islamophobic protests as "crap." Strike two.

See the problem? The purity police, who long ago excommunicated Romney as a closet moderate, will abide no nuance in the Republican field. If they ultimately allow a beleaguered Obama to run free on center ground, they'll have only themselves to blame.

The American Debate:

Chat live with Dick Polman at 1 p.m. Monday at