But while she has shown more willingness to chide her opponents more directly since her fourth-place finish in last week’s New Hampshire primary, her message is still largely free of the direct attacks that her rivals have embraced.

Her campaign has put a particular emphasis on courting Latino voters in Nevada, with whom aides believe she can outperform the candidates who leapfrogged her in Iowa and New Hampshire, including Mr. Buttigieg and Senator Amy Klobuchar. Her campaign on Monday also announced a “Latino Community Engagement Tour” in California.

Mr. Buttigieg campaigned in northern Nevada on Monday. At two events he was asked what he would do if he won the presidency but Mr. Trump refused to leave the White House.

“I guess if he’s willing to do chores, we could work something out,” Mr. Buttigieg said.

He followed up with a serious answer: The way to deprive Mr. Trump of the ability to claim electoral fraud, he said, is to win by a margin “beyond cheating distance.” He said he was “determined to build the broadest coalition,” a goal that has so far escaped him as he struggles, despite top finishes in the first two contests, to demonstrate support from nonwhite voters in polling of more diverse states like Nevada.

Mr. Buttigieg also released a new ad in Nevada that implicitly criticized Mr. Sanders, without naming him, as too far left to beat Mr. Trump. “We’re not going to do it by overreaching,” Mr. Buttigieg said in the ad. “We’re not going to do it by division.”