“When I began my service, what bound us as Republicans were fiscal issues, but we respected one another’s views and differences,” Snowe said in an interview. Today, “those who are involved have hardened and politicized their views; there’s no compromising on the issues. It becomes about political messaging, who can advantage themselves in the next election.”

The thin majorities each party holds in Congress has only amplified partisanship, though not congressional popularity. Just 13% of Americans approve of the job Congress is doing, according to a recent Gallup poll. Approval reached an all-time low during last year’s debt-ceiling debate, which featured a partisan standoff.

“Nothing is getting done, and it’s driving me insane,” said Crystal Cox, 38, an Indiana homemaker who was planning to vote for Romney, who she considered a moderate, until he appointed Rep. Paul D. Ryan of Wisconsin as his running mate. Cox opposes Ryan’s positions and said she would now vote for President Obama. “I was looking at Romney, thinking he’s more moderate, most likely to get things done,” she said.