PHOENIX — Senator Kelly, the Democratic incumbent, won his bid for reelection Friday in the crucial swing state of Arizona, defeating Republican venture capitalist Blake Masters to put his party one victory away from clinching control of the chamber for the next two years of President Biden’s term.

With Vice President Harris’ tiebreaking vote, Democrats can retain control of the Senate by winning either the Nevada race, which remains too early to call, or next month’s runoff in Georgia. Republicans now must win both those races to take the majority.

The Arizona race is one of a handful of contests that Republicans targeted in their bid to take control of the 50-50 Senate. It was a test of the inroads that Mr. Kelly and other Democrats have made in a state once reliably dominated by the GOP. 

Mr. Kelly’s victory suggests Democratic success in Arizona was not an aberration during the presidency of Donald Trump.

The closely watched race for governor between Democrat Katie Hobbs and Republican Kari Lake was too early to call Friday night. In the secretary of state’s race, Democrat Adrian Fontes defeated Republican Mark Finchem, a top 2020 election denier.

Mr. Kelly, a former NASA astronaut who’s flown in space four times, is married to the former Arizona congresswoman, Gabby Giffords, who recovered from a gunshot wound to the head during an assassination attempt in 2011 that killed six people and injured 13. Mr. Kelly and Ms. Giffords went on to co-found a gun safety advocacy group.

Mr. Kelly and Ms. Giffords were at an Elton John concert at Phoenix on Friday night when the Associated Press called the race, a campaign spokeswoman, Sarah Guggenheimer said. 

Maricopa County reported a large batch of results that increased Mr. Kelly’s lead and made clear Mr. Masters could not make up the difference with the remaining ballots.

“It’s been one of the great honors of my life to serve as Arizona’s Senator,” Mr. Kelly said in a statement. “I’m humbled by the trust our state has placed in me to continue this work.”

Mr. Kelly’s 2022 campaign largely focused on his support for abortion rights, protecting Social Security, lowering drug prices, and ensuring a stable water supply in the midst of a drought, which has curtailed Arizona’s share of Colorado River water.

With Mr. Biden struggling with low approval ratings, Mr. Kelly distanced himself from the president, particularly on border security, and played down his Democratic affiliation amid angst about the state of the economy.

He also styled himself as an independent willing to buck his party, in the style of Senator McCain.