Rep. Chris Van Hollen leads in a new poll. on October 16, 2015 (Photo by Marvin Joseph/The Washington Post) (Marvin Joseph/The Washington Post)

Rep. Chris Van Hollen is leading in Maryland’s Democratic primary race for the seat being vacated by Sen. Barbara A. Mikulski, according to a poll released Sunday by the Baltimore Sun.

Thus far, Rep. Donna F. Edwards of Prince George’s County has led in polls against Van Hollen, who represents Montgomery County, despite a severe financial disadvantage. But the Sun survey gives Van Hollen a 14-point lead over Edwards, 45 percent to 31 percent. That differs significantly from a Washington Post-University of Maryland poll in October in which Edwards bested Van Hollen by 10 points. In polling released by Edwards’s campaign in August, she led by five points.

The change could be a sign that Van Hollen’s advertising in the Baltimore media market and campaigning across the state have had an impact. He has more than 10 times as much money in his campaign fund as Edwards and far more support among the state’s Democratic establishment. The Sun found he led by a 2-to-1 margin in Baltimore, where neither candidate is very well known.

However, the polls also differ in methodology.

The Post and U-Md. contacted a random sample of registered Democrats, while the Sun identified likely primary participants from voting rolls. In the ­Post-U-Md. survey, Van Hollen performed better among Democrats ages 65 and older and among those who say they voted in the 2014 midterm elections — all of whom are more likely to turn out in a primary.

Edwards, like the Sun, polled likely voters. But she did not release the list of questions asked, and poll results from campaigns favor the candidate.

Turnout is expected to be low in the April 26 contest, but it will depend on how competitive the presidential primary remains at that point as well as the mayoral contest in Baltimore.

All three surveys found that, should he run, Rep. Elijah E. Cummings would best both Edwards and Van Hollen. Cummings, who represents Baltimore, has repeatedly said that he is still considering launching a campaign but has made no move toward a bid.