At one point during Wednesday’s Republican debate, Ben Carson was asked about his involvement with Mannatech, a nutritional supplements company that makes outlandish claims about its products and has been forced to pay $7 million to settle a deceptive-practices lawsuit. The audience booed, and Mr. Carson denied being involved with the company. Both reactions tell you a lot about the driving forces behind modern American politics.

As it happens, Mr. Carson lied. He has indeed been deeply involved with Mannatech, and has done a lot to help promote its merchandise. PolitiFact quickly rated his claim false, without qualification. But the Republican base doesn’t want to hear about it, and the candidate apparently believes, probably correctly, that he can simply brazen it out. These days, in his party, being an obvious grifter isn’t a liability, and may even be an asset.

And this doesn’t just go for outsider candidates like Mr. Carson and Donald Trump. Insider politicians like Marco Rubio are simply engaged in a different, classier kind of scam — and they are empowered in part by the way the grifters have defined respectability down.

About the grifters: Start with the lowest level, in which marketers use political affinity to sell get-rich-quick schemes, miracle cures, and suchlike. That’s the Carson phenomenon, and it’s just the latest example of a long tradition. As the historian Rick Perlstein documents, a “strategic alliance of snake-oil vendors and conservative true believers” goes back half a century. Direct-mail marketing using addresses culled from political campaigns has given way to email, but the game remains the same.