Sen. Bernard Sanders captured a surprise win in the Indiana primary Tuesday, giving his campaign more fuel to fight until the Democratic National Convention in July and frustrating Hillary Clinton, who desperately wants to shift into general election mode.

Networks called the race by 9:10 p.m. EDT, just over two hours after the Indiana polls closed. With 84 percent of the vote counted at 10 p.m., Mr. Sanders had 53 percent compared with 47 percent for Mrs. Clinton.

The Indiana win ends an impressive string of victories for Mrs. Clinton, who captured six of the past seven contests heading into Tuesday. The Sanders victory also prolongs a race that the former first lady is eager to put behind her as she turns her attention to presumptive Republican presidential nominee Donald Trump.

Despite having little realistic path to his party’s nomination, Mr. Sanders appears intent on remaining in the race to continue pushing Mrs. Clinton further left on issues such as Wall Street reform and income inequality.