MONTGOMERY AND Prince George’s counties have contributed heavily to what has become one-party Democratic rule in Annapolis: Not a single Republican state delegate or senator represents either of Maryland’s two biggest counties. That’s not healthy for those localities or for the state. Unfortunately, it’s also self-perpetuating: GOP candidates have been so marginalized that few have the money, political base and basic familiarity with state government to mount a credible campaign for office.

We make our endorsements in Maryland legislative races this year mindful of the imbalance in the State House and frustrated at the scarcity of credible Republican candidates. We do not offer endorsements in every district; rather, we’ve focused our attention on races where there is a choice between or among credible candidates. The names of candidates we’ve endorsed in Montgomery’s races appear below in bold type; our picks in Prince George’s will appear in the coming days.

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District 14: In the Senate race, Republican Frank Howard, a first-time candidate, has run a vigorous campaign while incumbent Democrat Karen S. Montgomery appears to be inert; her Web site has not been updated recently. Ms. Montgomery, who has served in the legislature since 2002 and was elected to the Senate in 2010, has been a marginal player in Annapolis, though she has been an advocate for seniors. Mr. Howard, a businessman, wants to repeal some of the legislature’s recent tax increases but is appropriately focused on using gas tax revenues to improve roads in a district that ranges from Silver Spring along the county’s eastern border.

In the House, three capable Democratic incumbents merit reelection in this district: Anne R. Kaiser, Eric G. Luedtke and Craig J. Zucker. Mr. Luedtke and Mr. Zucker are promising freshmen who haven’t yet made a major mark in Annapolis. Still, they are preferable to any of the three Republicans, who are well-meaning but very lightly versed in the issues and whose experience with state and local issues is scant.

District 15: Inveterate gadfly Robin Ficker, author of numerous anti-tax ballot questions, is the Republican candidate in the Senate, while his son Flynn is running for delegate. The two Fickers, who say they have knocked on 60,000 doors in the sprawling upcounty district over the past 18 months, strike a moderate stance on taxes. They say they would not seek the repeal of existing levies but would try to divert funds to adding road and light rail capacity in the Interstate 270 corridor. Republican Ed Edmundson, a first-time candidate for delegate, strikes similarly moderate positions.

However, they are up against formidable incumbents who deserve reelection: Brian J. Feldman, the incumbent senator, is former chair of the Montgomery House delegation. Appointed to the Senate seat in 2013, he has been a leader in advocating for Montgomery’s biotechnology corridor. In the House, Kathleen M. Dumais has been a smart and effective member of the Judiciary Committee, while Aruna Miller gained a spot on the powerful Ways and Means Committee in her first term. David Fraser-Hidalgo, who was appointed to Feldman’s seat, made a good start in the 2013-2014 session and is one of the legislature’s few Latinos.

District 16: In this competitive race for the House of Delegates, we endorse incumbent Democrat Bill Frick and two challengers, Democrat Marc Korman and Republican Rose Li.

Mr. Frick is a rising star in the legislature, a budget expert who has contributed on a range of issues. Mr. Korman, a lawyer, product of Montgomery County schools and party activist who has worked on Capitol Hill, has the makings of a productive legislator, especially on issues pertaining to Metro and transportation generally. Ms. Li, with degrees from the University of Chicago and Princeton University, is an impressive fresh face, the founder and manager of a small business involved in scientific writing and conferences. Ms. Li believes Montgomery County is not getting its fair share of state funds for school construction and other purposes, and she argues that a win by a moderate Republican like herself would inspire the Democratic delegation to fight harder with its leadership on behalf of local constituents.

District 19: Democratic incumbent delegates Benjamin F. Kramer and Bonnie L. Cullison make a strong team and deserve reelection. Maricé Morales, the third Democrat on the ballot, a young attorney and former House of Delegates staffer, is the person to join them. The lone Republican running in this three-seat district is Martha Schaerr, who doesn’t talk about her past work to overturn the state’s marriage-equality law in 2011 and 2012. Nor does she mention her 2007 push to include in the county’s sex education curriculum the erroneous information that homosexuality is a “choice.”

District 20: Of the three Democrats for delegate on the ballot in this district centered on Takoma Park, we endorsed just one, Sheila E. Hixson, a veteran incumbent, in the primary. In the general election we also endorse Democrat Will Smith and Green Party candidate Dan Robinson. Mr. Smith, a bright young lawyer, has served in the Department of Homeland Security and as an officer in the Navy Reserve, in addition to his extensive involvement in county affairs. Mr. Robinson, a thoughtful, experienced former Takoma Park city councilor and local businessman, advocates greater municipal control of resources currently allocated by the county.