Politico quotes from Senate leader Mitch McConnell’s new memoir, which contains a pertinent section on the deceit of hardline Republicans.

McConnell relates that when the upper chamber took up a deficit-reduction bill in 2005 — Republicans were in the majority at the time — Jim DeMint, then a senator for South Carolina, thanked McConnell for his work on the legislation, saying, “That was the best we could do.”

And then voted against it.

Hypocrisy

“This exchange perfectly illustrated the hypocrisy of DeMint and his whole enterprise,” McConnell writes in his book.

People like him were depending on me to pick up the pieces by brokering deals. He’d say it was the best we could do, privately, and then fundraise by blasting me for the same deals.

DeMint wouldn’t even be the worst of it. He paved the way for purists like Ted Cruz, who has made a career out of assailing his own party for supposedly betraying its conservative principles.

All or nothing

McConnell’s counterpart in the House of Representatives, John Boehner, resigned last year in desperation at his own all-or-nothing caucus.

Megan McArdle wrote for Bloomberg View at the time that the mistake Boehner’s Republican critics made was that they believed the Democrats would meet them halfway if they asked the impossible.

In reality, she argued, if you ask too much, the other side will probably decide that no deal is better than a deal at all.

DeMint’s successors have yet to accept that and learn to say yes if they’re offered 90 percent of what they want.

Until they do, pragmatists like McConnell will have the thankless task of keeping the government running.