There’s a double standard when it comes to religion and politics. Many people who claim to want the former out of the latter really only object to conservative religion advancing conservative politics. They have no problem with liberal Democrats who invoke Jesus Christ, quote Scripture, are members of the clergy or even, in a pinch, oppose same-sex marriage.

Liberal Democrats can even claim that their conservative opponents’ aren’t true Christians. But Jack Conway is learning that even this old double standard has its limits. Conway is the Democratic nominee for Senate in Kentucky. With his campaign in desperation mode, he released an ad that suggests his Republican opponent Rand Paul is anti-Christian.

According to the narrator, Paul was “a member of a secret society that called the Holy Bible ‘a hoax'” and “was banned for mocking Christianity and Christ.” Paul also stands accused of tying up a woman and making her worship “Aqua Buddha.” Oh, and he also would “end the deduction for religious charities.”

Well, the source for this last claim is Paul’s support for the Fair Tax, which does indeed end the deduction for religious charities — because it eliminates the federal income tax. Mike Huckabeee also backs the Fair Tax and while Huckabee has been known to support economic policy prescriptions that are unwise, no sane person has accused him of being anti-Christian.

The whole episode has turned out to be a bit much even for most liberals, who are rightly calling Conway out on the ad. Blogger Josh Marshall said the commercial “registered for me as somewhere between a hokey Tea Party ad and an SNL spoof.” Sen. Claire McCaskill (D-Mo.) called the ad “very dangerous” and said it “came very close to the line.”

Jason Zengerle of the New Republic described it as “the most despicable ad of this political season.” Zengerle is no Rand Paul enthusiast. In fact, he is the reporter who broke the Aqua Buddha story in GQ. Paul’s NoZe membership and college pranks don’t mark him as any less Christian than the Wittenberg Door. “Although the Conway campaign makes the NoZe Brotherhood sound like a bunch of pagans who got together to sacrifice small woodland creatures in tribute to the anti-Christ,” writes Zengerle, “the group was, in reality, the closest thing Baylor had to the Harvard Lampoon.”

Zengerle’s TNR colleague Jonathan Chait opined that “Rand Paul harbors a private contempt for Christianity” based on really little more than college-era letters Paul wrote about Ayn Rand. But there are lots of people who have imbibed the objectivist thinker’s individualism and libertarianism without embracing her anti-Christianity, probably in greater numbers than radical liberation theologians who square Marxism with Chrisitianity.

Even Chait pronounces Conway’s attack “the ugliest, most illiberal political ad of the year.” It’s also worth noting, as Chait compares Ayn Rand to Karl Marx, that while Whittaker Chambers envisioned Rand issuing the command “To a gas chamber — go!,” Marx’s disciples actually sent people there in large numbers.

Conway didn’t back down in a candidates’ debate Sunday. “Values matter,” he said, reiterating the charge. “Why did he freely join a group known for mocking or making fun of people of faith? And secondly, when is it ever a good idea to tie up a woman and ask her to kneel before a false idol called Aqua Buddha?”

“You demean the state of Kentucky. You embarrass yourself,” Paul shot back. Declaring himself “a pro-life Christian,” he continued, “You know how we know when you’re lying? Your lips are moving. You’re accusing me of crimes. Do you know nothing about the process? You’re going to stand there and accuse me of a crime from 30 years ago from some anonymous source? How ridiculous are you? You embarrass this race.”

Paul faced similar charges in the Republican primary. His opponent Trey Grayson — who has since endorsed him for Senate, like most of his GOP detractors — attacked him on abortion and other social issues, employing caricatures of libertarianism. But those caricatures apply even less to him than they did to his father, prompting James Dobson to switch endorsements from Grayson to Paul once he learned the facts. Dobson called his initial endorsement “an embarrassing mistake.”

An even bigger defining moment in the primary campaign when Grayson tried to associate Paul with those who believe the United States is to blame for the 9/11 terrorist attacks. Rather than defend his father’s views of blowback, Paul simply hit back: “Trey Grayson, your shameful TV ad is a lie and it dishonors you.”

As the polls tighten in the Kentucky Senate race, it remains to be seen whether Paul’s counterpunching can prevail again. But the political climate might prompt Conway to hedge his bets by praying to Aqua Buddha.