Former D.C. Mayor Vincent Gray departs after casting his ballot at Precinct 113 in Ward 7 in Washington. (J. Lawler Duggan/For The Washington Post)

Democrats who vote in the District’s primary Tuesday will decide the makeup of the D.C. Council for the next two years, including whether former mayor Vincent C. Gray will return to public life.

Gray is seeking a political comeback as a Ward 7 council member after federal prosecutors announced in December that they would halt a five-year investigation into illegal financing of his successful 2010 run for mayor. Six of Gray’s friends and associates pleaded guilty in the scandal; he was never charged.

Because three out of every four voters in the District are registered Democrats, the primary election is tantamount to the general election. Polls in the city open at 7 a.m. and close at 8 p.m.

In Virginia, there are contested primaries in three of the state’s 11 congressional districts, some of which were turned upside down by a recent court ruling redrawing the congressional district map. Polls are open from 6 a.m. to 7 p.m.

Ward 7 candidate Yvette Alexander poses for a photo with a ballot station worker inside the gymnasium of the Highlands Elementary School on Tuesday. (Christian K. Lee/The Washington Post)

Rep. J. Randy Forbes (R-Va.) opted against running for reelection in his Richmond-area 4th District and is instead trying for a win in the 2nd District, anchored by Virginia Beach. He faces a challenge from Del. Scott W. Taylor (R-Virginia Beach), a former Navy SEAL, and attorney Pat Cardwell.

Democrats think they have a good chance of turning Forbes’s old district blue. Under the new boundaries, the district gained African American voters who reliably vote for Democrats, according to exit polls. In that district, Sen. A. Donald McEachin (D-Henrico) is taking on Ella Ward, a council member in Chesapeake City; both candidates are black.

In addition to a contested GOP primary in the 4th District, Rep. Bob Goodlatte (R-Va.) will face a lesser-known challenger, Harry Griego, in the 6th District, which includes Roanoke and Lynchburg.

Locally, there is also an unusual Democratic primary, with the sitting Arlington County Board chair facing a primary challenge for the first time in 14 years.

Libby Garvey , a first-term incumbent, aggravated party activists two years ago when she supported a Republican running as an independent against another Democrat in a County Board race. Newcomer Erik Gutshall has been hammering away at Garvey’s record on the board.

Since Virginia voters do not register by party, the primary is open to any registered voter in the county. Garvey has been soliciting Republicans and independents as well as her Democratic supporters. Gutshall is relying on motivated Democratic stalwarts to vote.

In the District, Democrats will also weigh in on the race for their party’s presidential nomination, although it seems a futile exercise, as front-runner Hillary Clinton secured enough delegates last week to vanquish Sen. Bernie Sanders of Vermont.

Former president Bill Clinton, in the District on Saturday, appeared at a farmers market on Capitol Hill to meet voters and try to “stir up some interest” in Tuesday’s vote.

The race between Gray and incumbent D.C. Council member Yvette Alexander will be decided at the ward level, with voters mostly east of the Anacostia River making the call.

With only a handful of such intensely local contests in play, Anita Bonds, chairwoman of the D.C. Democratic Party on Monday recorded a robo-call delivered to 80,000 homes before dinner, urging Democrats to turn out and vote.

“It’s important that you express your right that so many people have died for,” Bonds, an at-large D.C. Council member, said on the call.

A spokesman for Bonds said the call was intended to be neutral, not favoring any candidate, and was paid for by the party.

D.C. Democrats have struggled with historically low turnout in recent primaries.

In 2014, when the mayor’s office was up for grabs, turnout was the party’s worst in at least three decades, with about a quarter of registered voters going to the polls. Before that, turnout in a mayoral race had never dipped below 30 percent of registered voters.

Political observers attributed part of the low turnout that year to the date — April 1, the earliest a local primary had ever been held. But some voters blamed continued scandals in D.C. politics and others said the city’s improving economy may have muted concerns about the functioning of city government.

Last year, however, turnout was even weaker for a special election to fill openings created by Muriel E. Bowser’s ascension to the mayor’s office and Marion Barry’s death.

A rematch in that race, between incumbent LaRuby May and challenger Trayon White, could be the closest contest Tuesday. In the crowded special election last April, May topped White by fewer than 100 votes.

In Ward 4, Council member Brandon Todd, a former campaign finance chairman for Bowser, faces his biggest threat from Leon Andrews, who has questioned Todd’s support for the Pepco-Exelon merger and close backing of other Bowser policies.

In the at-large race, Council member Vincent Orange is facing challengers Robert White and David Garber.

Jenna Portnoy and Patricia Sullivan contributed to this report.