Rep. Chris Van Hollen (D-Md.) (Amanda Voisard/For the Washington Post)

REPS. DONNA EDWARDS and Chris Van Hollen, rivals for the Democratic nomination for U.S. Senate in Maryland, are astute, accomplished lawmakers. Both are liberals; both have represented the Washington suburbs for multiple terms in the House; both have been allies to President Obama. Each has received our endorsement in the past, and each is qualified to serve in the Senate.

That said, the two offer Maryland voters a stark choice, and not only a stylistic one, between the courtly, understated Mr. Van Hollen and the forthright, unwavering Ms. Edwards. The main difference is that Mr. Van Hollen — pragmatic, detail-oriented, agile — could be a real force for accomplishment. By contrast, Ms. Edwards, whose many attributes do not include a gift for team play, would reinforce Congress’s tendency toward stalemate along partisan lines.

If relieving the dysfunction in Congress is important — and it is — then Mr. Van Hollen, a gifted legislator, is the better candidate, and the one who could contribute meaningfully to breaking Washington’s legislative logjam.

The ideological distinctions between Mr. Van Hollen and Ms. Edwards are minuscule. Both have embraced core Democratic values. Both regard government as a force for social progress and equality. Both are pro-labor. Both worry about climate change.

But Mr. Van Hollen has consistently earned a seat at the table where consensus might be forged. Elected to the House in 2002, he ascended rapidly through the Democratic leadership ranks and became the party’s senior member of the Budget Committee. He is the author of elegant legislation to combat climate change that might, if sanity ever returns, stand a chance of passage: a carbon tax bill that would send all revenue back to taxpayers (pleasing Republicans) in a highly progressive way (pleasing Democrats).

As a key lieutenant to House Democratic leader Nancy Pelosi, he has been at the center of negotiations on budget reform and deficit reduction. That role allowed him to help fend off Republican threats to shut down the government. It also brought some political hazards, as when Mr. Van Hollen suggested, in 2012, that a combination of new revenue and slower growth of entitlement programs was the “right way to go” for a bipartisan budget deal. That statement was arithmetical common sense to tackle the nation’s long-term deficit and debt. Yet it was attacked as heresy by Democrats to whom compromise is unthinkable — including Ms. Edwards. That makes her part of the problem in Washington.

Elected in 2008, Ms. Edwards has brought a valuable perspective to Congress. As an African American single mother and a local activist who had tussled with big developers, she played up her outsider status while insisting she also could work the system to achieve gains on health care, green building standards and NASA budgets. No one doubts her policy chops in her areas of interest.

Yet Ms. Edwards has alienated officials, including from her base in Prince George’s County, who might have been natural allies. Even some admirers criticize her for aloofness from the details of local problem-solving and for running an office notorious for inattention to constituent services and teamwork.

The flip side of Mr. Van Hollen’s ascension into leadership has been a reluctance to stake out strong stands independent of his party. To make a lasting mark in the Senate, he will have to do that at times. Undeniably, though, Mr. Van Hollen has the potential to be a very good senator. On that basis we endorse him in the April 26 primary.