Thomas Kean

Rebecca Bennett, a former U.S. Navy helicopter pilot and aircraft commander, beat three opponents on Tuesday to win the Democratic nomination to run in November against Representative Thomas Kean Jr., a New Jersey Republican who has been missing from Congress for nearly three months.

The race is expected to be among the country’s most contested midterm matchups. Democrats see Mr. Kean’s seat in New Jersey’s Seventh Congressional District as a potential pickup as they seek to retake the House and check President Trump’s power in Washington.

Ms. Bennett was leading her closest primary opponent, Tina Shah, by roughly 27 percentage points when The Associated Press called the race in her favor an hour after polls closed.

She thanked her supporters gathered in Bridgewater, N.J., in a rousing address.

“If this group of badass American patriots can get a political outsider — a 2010 Honda Accord-driving, Navy-veteran mom — to win in one of the most competitive primaries in the country, we are going to flip this seat,” Ms. Bennett said.

“Hard does not scare me,” she said, adding: “We cannot just be anti-Trump and anti hate. We have to be for something. We have to solve the problems that we are all facing in our everyday lives.”

Mr. Kean, 57, had no challenger in Tuesday’s Republican primary. But intrigue over an unexplained health condition that has caused him to vanish from public life since the middle of March has overshadowed much of the debate in recent months. He has missed more than 100 votes during his absence, at a time when Republicans hold a narrow House majority and are working to advance the president’s agenda ahead of the midterm elections.

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