The nearly forgotten candidacy of Tim Pawlenty offers a clue. Once upon a time a conservative governor from a swing region with a record of working across the aisle might have gained traction.

But in a party that has come to loathe compromise, Pawlenty didn’t have the gumption to run on his record, and he couldn’t sell himself as less nice and more ideologically pure than he really was. When he couldn’t bring himself to be mean to Romney in an early New Hampshire debate, he was finished.

The Republican ideology of no new taxes, ever, is a straitjacket. But even more dispositive is the conviction that reaching across the aisle is weak and treasonous.

Until that conviction fades, politicians who want to get things done, and would know how to strike deals in the nation’s interest, may stay on the sidelines.