THE MARYLAND SUBURBS of Washington are so heavily Democratic that serious and substantive Republicans tend not to bother running for Congress. This Nov. 4 three of the four Democratic incumbents — Reps. Donna Edwards (District 4); Steny Hoyer (District 5) and Chris Van Hollen (District 8) — face only nominal opposition.

Only first-term Democratic Rep. John Delaney faces a well-funded GOP opponent. Dan Bongino is a former Secret Service agent turned security consultant and guest host on right-wing radio talk shows. In our view, Mr. Delaney is not only the clearly superior candidate; he is also one of the most impressive new lawmakers in Congress. We endorse him.

First, the other three incumbents, all of whom are exceptionally capable — fortunately for Marylanders. We disagree with Ms. Edwards on a range of issues, especially in the arena of foreign policy and trade, but she’s an effective advocate and eloquent voice for her left-leaning positions on domestic matters and for her constituents. Mr. Hoyer is the second-ranking House Democrat and a voice of sanity on Capitol Hill. Mr. Van Hollen, whose policy expertise is as formidable as his political savvy, has risen meteorically in his party’s leadership and recently proposed a cogent, market-based strategy for reducing carbon emissions.

Mr. Delaney represents Maryland’s 6th District, which stretches from Montgomery County west to rural Garrett County. He is the only member of Congress who is a former chief executive of a publicly traded company (a bank).

Unusually for a Capitol Hill freshman, Mr. Delaney has managed to make a mark and gain broad respect among leaders of both parties. He has done so the old-fashioned way, with detailed legislative proposals — on housing and infrastructure finance, among other issues — while largely avoiding partisan rhetoric.

Leveraging his experience in finance, Mr. Delaney authored a bill with dozens of co-sponsors — including almost an equal number of Republicans and Democrats — to establish a national infrastructure bank to pay for road, rail, energy and other major projects with the help of profits repatriated to the United States by multinational companies.

He has broken with his party leadership to vote with Republicans on occasion, drawing attacks from liberals but establishing himself as one of a dwindling breed of lawmakers with a plausible claim to centrism.

Mr. Bongino, who mounted an unsuccessful campaign for the U.S. Senate right after retiring from the Secret Service in 2011, has a flair for self-promotion based on an aggressive, highly partisan rhetorical style. If elected, he would be a polarizing force in a Congress that hardly needs more of that. On immigration, he favors continued deportation and rejects any compromise that would lead to legalization for undocumented workers. On fiscal issues, he favors trimming entitlements but rules out any realistic deal with Democrats that would yield new revenue. It’s impossible to imagine him working across the aisle, as Mr. Delaney has done.

Voters who hope for legislators who can break the paralysis in Congress should support Mr. Delaney.