AGAINST A backdrop of presidential primary choices that strike many Americans as uninspiring or alarming, voters in the Maryland suburbs have reason to feel fortunate, at least in this respect: Their options in a pair of open-seat congressional races include candidates who are actually stellar.

In both districts — the 4th, which includes much of Prince George’s County, and the 8th, which includes a chunk of Montgomery — the fields in Tuesday’s Democratic primaries, whose winners will be heavy favorites in November, are strong and deep. (The incumbents, Reps. Donna Edwards in the 4th and Chris Van Hollen in the 8th, are rivals in the Democratic primary for U.S. Senate.)

In the 4th District, our choice is Joseline Peña-Melnyk, a Dominican immigrant and former public defender and federal prosecutor who is among the most widely admired members of the Maryland state legislature, where she has represented a district in Prince George’s since 2007.

Ms. Peña-Melnyk, who overcame an impoverished childhood to make her way through college and law school, is a force of nature with exceptional reserves of vigor, enterprise and empathy. Although she casts herself as an outsider unafraid to take on the state and local Democratic establishments, which she has done, she also has been an effective legislator in Annapolis and could be in Congress, too. No one will outwork her or better attend to the needs of constituents.

In the 8th District, our pick is Kathleen Matthews, a veteran television anchor-turned-corporate executive with deep knowledge of the district and of policy. Ms. Matthews, though a first-time candidate, has run a smart, substantive campaign that suggests she could be a leader on Capitol Hill and help Maryland’s congressional delegation continue to punch well above its weight.

Each faces formidable rivals. In the 4th District field, Anthony G. Brown, formerly a state lawmaker and Maryland’s lieutenant governor, and Glenn Ivey, the former top prosecutor in Prince George’s, are capable, serious candidates. In the 8th District race, state Sen. Jamie Raskin, a champion of liberal causes in the state legislature, is highly esteemed by constituents and colleagues alike.

All of the above would make fine additions to Congress. We think Ms. Peña-Melnyk and Ms. Matthews would make excellent ones. What the two women share is a devotion to their communities, along with professional success that is the product of moxie and hard work.