Angela Alsobrooks Defeats David Trone in Maryland Democratic Senate Primary

Angela Alsobrooks, the Prince George’s County executive, won the Democratic primary for Maryland’s Senate seat on Tuesday, setting up a showdown with a popular Republican former governor that could determine control of the chamber.

The Associated Press called the race on Tuesday night for Ms. Alsobrooks, 53, who defeated Representative David Trone, a wealthy congressman who spent more than $61 million of his own money on the race. Mr. Trone outspent Ms. Alsobrooks by a nearly 10-to-1 ratio.

She is trying to become the first Black woman to represent Maryland in the Senate. The chamber now has just four Black members, three men and one woman, Senator Laphonza Butler, who has made it clear she will leave at the end of her term in January.

While Ms. Alsobrooks, a former prosecutor, trailed Mr. Trone early in the race, she was buoyed by widespread support among Maryland’s Democratic elected officials, who rallied around her campaign.

She will now face Larry Hogan, the former Maryland governor, in what will be a closely watched race. Mr. Hogan was recruited to run by Senator Mitch McConnell of Kentucky, the minority leader, as Republicans try to recapture the Senate.

Democrats and three independents who largely vote with them now control the chamber 51 to 49, but Republicans are favored to pick up West Virginia, increasing the need for Democrats to hold Maryland.

Ms. Alsobrooks and Mr. Hogan will compete to replace Senator Benjamin L. Cardin, who is retiring after holding the seat since 2007.

The primary between Ms. Alsobrooks and Mr. Trone turned negative as it tightened, splitting Democrats in Congress and beyond. A competitive primary was a rarity in Maryland, a reliably Democratic state that has not had a Republican senator in nearly four decades. Mr. Hogan’s decision to enter the race changed all that.

Mr. Trone scored endorsements from congressional leaders, who were eager to have a wealthy candidate who could fund his own Senate run as they embark on a costly battle in several competitive states to keep control of the chamber. But all but one Democrat in the state’s congressional delegation backed Ms. Alsobrooks.