Rep. Elijah Cummings (Melina Mara/The Washington Post)

Rep. Elijah E. Cummings (D-Md.) announced Tuesday that he will not seek the Senate seat being vacated by retiring Sen. Barbara A. Mikulski (D-Md.), saying he “can best serve the people of our city, our state and our nation by continuing my work in Congress.”

Cummings, a 10-term congressman from Baltimore, had agonized publicly for months over whether to join two other House Democrats in a primary battle for the Senate. A key figure in calming protesters after last year’s Baltimore riots, he was reluctant to leave the inner-city congressional district he has represented since 1996 to try for a higher-profile, and arguably more powerful, spot in the Senate.

Ultimately, unlike Reps. Chris Van Hollen and Donna F. Edwards, Cummings decided not to give up his leadership spot in the House for a chance at a Senate perch. Instead, he will seek reelection to Congress in November.

“When you’re leading in the polls by more than double digits, you have to take it into consideration,” Cummings said in an interview. “[But] I had to do what would allow me to be most effective and efficient at representing my constituents.”

Polls have consistently shown that Cummings, who is the ranking Democrat on the House Oversight Committee, would lead in a race against Edwards and Van Hollen.

A Baltimore Sun poll conducted after Van Hollen began a major ad blitz in Baltimore last fall found that 40 percent of Democratic primary voters still would choose Cummings.

However, Cummings is considered a relatively weak fundraiser and has not faced a competitive race in years. Although he ended last year with over a million dollars in his campaign bank account, Van Hollen has more than three times that amount in his coffers.

Cummings’s decision means that for the first time in decades, Democrats in Maryland will elect a Senate nominee from the Washington suburbs. Van Hollen’s congressional district is based in Montgomery County, while Edwards represents Prince George’s County and part of Anne Arundel County.

Two of the Republicans running for the seat — attorney and speechwriter Chrys Kefalas and state Del. Kathy Szeliga — are from the Baltimore area.

Baltimore has emerged as the key battleground in the Democratic primary campaign. Emily’s List, a Democratic women’s group, responded to Van Hollen’s advertising with its own Baltimore television barrage touting Edwards. Van Hollen has since begun a new round of Baltimore-focused ads. With Cummings officially out, those efforts will likely intensify.