U.S. Rep. Donna Edwards led Rep. Chris Van Hollen in a recent poll, despite Van Hollen having endorsements from a slew of prominent Democrats. (TWP)

Maryland Senate President Thomas V. Mike Miller Jr. has joined the ranks of prominent politicians backing Rep. Chris Van Hollen in the state’s tightly contested Democratic primary for an open U.S. Senate seat.

Miller (D-Calvert), the longest-serving state Senate president in the nation, said in an interview that Van Hollen’s deep ties with Maryland’s political establishment and his experience driving legislative initiatives would make him a more effective leader than his opponent, U.S. Rep. Donna F. Edwards.

“He’s the person I would want making policy on Capitol Hill,” Miller said. “He hasn’t asked me to endorse him per se, but in terms of the two, in terms of making things happen, I’m going to be very supportive of him.”

Van Hollen served 12 years in the Maryland General Assembly before winning election to the U.S. House in 2003. Edwards, by contrast, was a lawyer and community activist who in 2008 ousted a Democratic incumbent and became the first African American woman to represent Maryland in Congress.

Miller’s backing gives Van Hollen another establishment ally in his bid to fill the seat of retiring U.S. Sen. Barbara Mikulski (D), a legendary figure in Maryland politics.

Among those in the party who have endorsed the congressman are Maryland Attorney General Brian E. Frosh, Montgomery County Executive Isiah Leggett, Prince George’s County Executive Rushern L. Baker III and state Del. Maggie L. McIntosh (Baltimore).

Van Hollen also has a substantial fundraising advantage over Edwards, whose key supporter is Emily’s List, which backs the candidacies of Democratic women who support abortion rights.

Polls have shown a tight race, with Edwards edging ahead by six percentage points in the latest survey by the Baltimore Sun and the University of Baltimore. The primary is April 26.

Edwards has expressed few policy differences with her opponent, but she has said she would bring a unique and much-needed perspective to the U.S. Senate as a black, single mother. Only one woman of color, Sen. Mazie Hirono (D-Hawaii), serves in the chamber.

“When you have diverse voices . . . you make better decisions,” Edwards said Saturday at a campaign event in Prince George’s.

Van Hollen and his supporters have touted his legislative accomplishments — and his relationships with lawmakers in Congress and the state legislature — as his strengths.

“I like them both, but in terms of a leader who has been born to the job . . . he’s an accomplished leader,” Miller said.

“He gets along with everybody . . . he can forge coalitions and make things happen.”