Tammy Murphy, New Jersey’s first lady, has ended her run for a U.S. Senate seat now held by the state’s embattled senior senator, Robert Menendez, she announced on Sunday in a video posted to social media.

Ms. Murphy said that she had concluded that continuing to compete in the Democratic primary against Representative Andy Kim, a third-term congressman from South Jersey, would mean waging a “very divisive and negative campaign.”

She was unwilling to do that, she said, and instead decided to suspend her campaign and to “focus entirely on re-electing President Biden” and other Democrats.

“With Donald Trump on the ballot and so much at stake for our nation, I will not in good conscience waste resources tearing down a fellow Democrat,” she said.

An aide said that Ms. Murphy, the wife of Gov. Philip D. Murphy, held a meeting with county Democratic Party leaders at 2 p.m. on Sunday before making a final decision and notifying her campaign staff members.

Candidates who plan to run in June’s primary are required to file petitions with at least 1,000 signatures by the end of the day on Monday. Ms. Murphy’s decision on the eve of that deadline means that her name will not appear on the primary ballot.