SEVEN YEARS AGO, as Robert L. Ehrlich Jr., the first Republican governor of Maryland in half a century, prepared to seek a second term, party leaders spoke hopefully of breaking the Democrats’ stranglehold on state politics. It didn’t happen. Mr. Ehrlich lost his race and, since then, Republican candidates have embraced the national GOP’s rightward tilt and proved a poor fit for Maryland’s centrist and liberal voters.

This year’s crop of Republican candidates for Congress in Maryland’s suburbs illustrates the problem. All of them oppose any deal to reduce the nation’s deficit that includes new revenue. Bipartisan compromise is off-limits to these Republicans — the absolutist approach that has led to impasse in the current Congress.

We have written separately in support of John Delaney, the pragmatic Democrat challenging an ineffectual 20-year Republican incumbent, Rep. Roscoe Bartlett, in the redrawn 6th District, which stretches from near the Beltway to Maryland’s border with West Virginia.

In three other districts, Democratic incumbents face challenges.

The least entrenched of these incumbents is Rep. Donna Edwards, elected in 2008 in Maryland’s 4th District, which includes parts of Prince George’s and Anne Arundel counties. Ms. Edwards is an eloquent lawmaker — she was among those chosen to address the Democratic National Convention in Charlotte — and an effective advocate for liberal causes.

But she has had a prickly relationship with her party’s leadership, and her office has a poor reputation for constituent services. She has a checkered record on free-trade issues, a stance affording an angle of attack for an able opponent.

Ms. Edwards’s Republican challenger, Faith Loudon, a longtime party activist, is not that opponent. Her grasp of issues is thin. Even in a less Democratic-leaning district than the 4th, Ms. Loudon would make a weak candidate. We endorse Ms. Edwards.

A more plausible Republican candidate, state Del. Anthony J. O’Donnell (Calvert), is on the ballot in the 5th District, consisting of parts of Prince George’s and Anne Arundel counties, which Rep. Steny Hoyer has represented for more than 30 years. Mr. O’Donnell is minority leader in the House and an affable fellow. But his over-the-top rhetoric about Mr. Hoyer, coupled with his decision to sign a pledge never to raise any tax, suggests he would be unable to work across the aisle in Congress.

By contrast, Mr. Hoyer, the second-ranking Democrat in the House of Representatives, is an effective, highly sensible lawmaker with a record of getting things done. He deserves reelection.

In the 8th District, which takes in parts of Montgomery and Frederick counties, Rep. Chris Van Hollen, who is completing a decade in office, is being challenged by Kenneth R. Timmerman, a journalist and an author. Mr. Timmerman is knowledgeable about the Mideast, particularly Iran. But his assessment that the Obama administration is turning America into a European-style welfare state is a cartoonish distortion, as Mr. Timmerman, who has spent much of his life in France, should know.

We support Mr. Van Hollen, an adept legislator who vaulted to the ranks of leadership in the House. He has been at the center of efforts to forge a compromise on long-term debt reduction, and if any such deal can be struck, Mr. Van Hollen is likely to be one of its authors.