Reps. Donna Edwards and Chris Van Hollen are neck and neck in a new Senate poll. (The Washington Post)

The Democratic primary for Maryland’s open Senate seat is now a dead heat between Reps. Donna F. Edwards and Chris Van Hollen, according to a poll released Tuesday morning.

The survey, conducted by Gonzales Research & Marketing Strategies over the past week, finds Van Hollen winning 38 percent of likely voters in the April 26 Democratic primary, and Edwards winning 36 percent, within the poll’s margin of error.

Those results are good news for Edwards, who in fall polling had dropped far behind Van Hollen. A Baltimore Sun survey taken in November gave Van Hollen a 14-point lead.

The Sun poll came after Van Hollen launched a $1 million advertising campaign in Baltimore, before any ads supporting Edwards were aired. But the national women’s group Emily’s List, which is backing Edwards, responded with its own $1 million ad buy on her behalf.

The Gonzales poll suggests that the investment has paid off. However, Van Hollen has since begun airing a new round of television ads, and Edwards has not. Her campaign does not have the funds to do so without outside help. In October, when financial reports were last released, Van Hollen had about $4 million in the bank and Edwards had less than $400,000.

“We’re pleased that Chris Van Hollen has maintained his lead, despite the million-dollar blitz of Super PAC advertising,” Van Hollen spokeswoman Bridgett Frey said in a statement.

The Gonzales survey shows an electorate that is polarized along racial and geographic lines. Edwards has a 50-point lead among African American likely Democratic primary voters, while Van Hollen has a 40-point lead among white likely Democratic primary voters.

The poll did not include the Republican primary, which has drawn three candidates so far: state House of Delegates Minority Whip Kathy Szeliga (R-Baltimore County); Chrysovalantis Kefalas, who works for the National Association of Manufacturers and is from Baltimore; and Richard J. Douglas, a former Pentagon official and lawyer from Montgomery County.

Edwards has a 26-point lead in the city of Baltimore, and Van Hollen leads by 16 points in the Baltimore suburbs. She garnered 68 percent support in her home county of Prince George’s, and he drew 60 percent in Montgomery County, his home base.

In the rest of the state, where there are fewer Democrats in general, Van Hollen outpolled Edwards 49 percent to 24 percent.

“Despite Congressman Van Hollen’s $1.5 million dollar ad campaign, Donna’s momentum is growing,” Edwards spokesman Benjamin Gerdes said in a statement.

Edwards has repeatedly argued that the voice of a black woman is needed in the Senate — especially to fill the seat of retiring Sen. Barbara A. Mikulski (D), the longest-serving woman in congressional history.

Van Hollen has countered that legislative accomplishment matters more than identity. He has won endorsements from far more elected officials in the state, including prominent female and African American leaders.

Gonzales polled 402 Democratic primary voters between Jan. 11 and 16, using both landlines and cellphones. The overall margin of error is plus or minus five percentage points.