A poll of Maryland Democrats commissioned by Rep. Elijah E. Cummings shows him ahead of the two declared candidates in the race to succeed retiring Sen. Barbara A. Mikulski (D).

The March poll, details of which were shared with The Washington Post, show Cummings supported by 29 percent of likely primary voters, followed by Rep. Donna F. Edwards with 23 percent and Rep. Chris Van Hollen with 22 percent.

Sixty-three percent of poll respondents have a favorable view of Cummings, compared with 48 percent for Van Hollen and 45 percent for Edwards. His name recognition is at 74 percent, compared with Van Hollen at 56 percent and Edwards at 52 percent.

The margin of error is plus or minus 3.7 percentage points.

Cummings, who is from Baltimore, has said he is carefully weighing whether to enter the primary. He declined to comment Wednesday, and several people who have spoken to him recently said he has yet to make up his mind.

According to the survey, Cummings does better in the Washington-area media market than his rivals — who are based in the D.C. suburbs — do in Baltimore.

Private polls released publicly tend to slant toward the politician favored by whoever commissioned the poll, and in general are not considered as reliable as surveys conducted by independent organizations.

Cummings pollster Mark Mellman, however, is a respected veteran in Democratic politics.

The poll his firm conducted included 700 likely primary voters who were contacted on land lines and cellphones. Sixty percent were female, 36 percent were African American, and 50 percent came from the Baltimore market. Those numbers closely track the those from a 2008 exit poll, the last done in a Maryland primary during a presidential election year.

Neither Edwards nor Van Hollen has polled the race. Van Hollen launched his campaign a mere two days after Mikulski announced her retirement. Edwards followed a week later, with the encouragement of national progressive groups.

Cummings, like Van Hollen and Edwards, would have to forgo running for another term in Congress to run for Senate in 2016. If all three are in the race, that would mean certain turnover in three of Maryland’s eight congressional seats.

Van Hollen has flexed his muscle early in terms of fundraising, putting $1.2 million over the past three months into what is now a $2.7 million war chest. By the end of last year, Cummings had nearly $900,000 on hand, far more than the $30,000 Edwards reported. In the two weeks after her announcement, Edwards raised $335,000, her campaign said Friday.

“Cummings comes to the table with a lot of strength,” said one Democratic strategist who has worked in Maryland politics but was not authorized to speak publicly on the race. “The question for him is how he is as a fundraiser — will he able to raise the resources necessary to run in a statewide race?”

Cummings has been elevated by his role as ranking Democrat on the House Oversight and Government Reform Committee, where he sparred frequently with former chairman Darrell Issa (R-Calif.). Last March, a video of Issa cutting off Cummings’s microphone went viral; the Republican later apologized.

The power that Cummings yields in the House might also be a reason to stay out of an expensive, nasty Senate race.

As the panel’s ranking minority-party member, Cummings is “a very important first line of defense for Democrats right now in Congress,” said Rep. Gerald E. Connolly (D-Va.), who sits on the oversight committee. “That’s obviously got to weigh on him. Does he want to walk away from that?”

Cummings and Edwards are African American, and a Cummings campaign could cut into Edwards’s support with the black voters who make up a large percentage of Maryland’s Democratic primary electorate.

But his popularity could also hurt Van Hollen, who has closer ties to many politicians in the state than Edwards, but he does not go back as far and in as many different circles as Cummings.

Maryland’s two U.S. Senate seats have been held by politicians from the Baltimore area in recent decades. So far, no Baltimore-area candidate has entered the race to succeed Mikulski, although former lieutenant governor Kathleen Kennedy Townsend (D) is also considering a bid. Neither Edwards nor Van Hollen has made significant inroads so far with politicians and activists from Baltimore.

“As soon as Cummings makes his decision, they’re going to start reaching out in earnest,” said Rick Abbruzzese, a longtime aide to former governor Martin O’Malley (D). “A huge part of the game will be played up here in the Baltimore metro area, and they’re going to have to do that — and quickly.”

John Wagner contributed to this report.