Not big on scripts or talking points, Bartlett has also often been prone to gaffes. During this past election, he associated student loans with Nazi Germany. He later apologized for the remark.

Bartlett ran unsuccessfully for the U.S. Senate in 1980 and the House in 1982. A decade later, he emerged to challenge Democrat Beverly B. Byron, who had represented Western Maryland for 14 years. Byron was upset in the Democratic primary by Thomas H. Hattery, a more liberal candidate who drove independent Democrats toward the little-known Bartlett.

Over the past year, several state Democrats who supported the redistricting quietly lamented that it was Bartlett who would be forced out.

"While Roscoe Bartlett and I have different ideas for how we can keep our state and country moving forward, we have worked together to address important issues for Maryland," said Rep. Steny H. Hoyer, the Southern Maryland Democrat and House minority whip. "Despite our differences, he has been a dedicated public servant who worked hard on behalf of his constituents."

Bartlett's Washington office was packed one day last week with staff members, many of whom were visiting from district offices to have a final picture taken with their boss. Others were there to begin the transition process. Some were teary-eyed.

Delaney will be sworn in come January. Until then, Bartlett will have a role to play — and votes to take — as lawmakers wrangle over a way to avoid the year-end combination of tax increases and automatic spending cuts known as the "fiscal cliff." The congressman wouldn't say directly whether he would take a more centrist approach to those issues given the election's outcome.

"It would be nice if we vote on those things in the lame-duck [session], but I don't think we will," he said. "I think what we're going to do in the lame-duck is simply push it off until next year."

As for the broader issues at stake, Bartlett expressed concern about the willingness of the colleagues he is leaving behind to reach a compromise.

"The two sides have to come together," he said. "It would be nice if you ran as a Democrat or Republican and you came to Congress as an American and just kind of left partisanship at the door."