President Donald Trump’s efforts to alter how elections are run faced an avalanche of setbacks last week, as Republican senators rebuffed him and court after court hindered his administration’s plans to, as one judge put it, undercut “the sacred right to vote.”

The pushback has infuriated the president, who has ramped up his threats and demands as he openly grows increasingly worried about the investigations and impeachment that could come if Democrats win control of Congress.

But with the general elections just four months away, Trump is racing the clock as states make final preparations for early voting.

The urgent push to change election rules by several arms of the federal government has created a volatile sea of shifting and contested election policies, many of which are before the courts. The climate of uncertainty is creating headaches for election officials and risks confusing voters, reanimating conspiracy theories about rigged elections and spurring postelection disputes.

“The administration is doing as much as possible to inject chaos into the election cycle,” said Wendy Weiser, vice president for democracy at the Brennan Center for Justice at New York University, a voting rights organization that has sued the administration over election policies. “A top priority for this administration is to try to interfere in this election.”...

Courts dealt Trump five adverse rulings last week, the first coming on Monday when a judge barred using a federal immigration database to determine voter eligibility. U.S. District Judge Sparkle L. Sooknanan determined the use of the Department of Homeland Security database violates federal privacy laws and was responsible for revoking the voter registrations of some citizens who were wrongly listed as noncitizens......

Election officials have little time to adjust to any new voting policies because they must start sending mail ballots for the general election to military and overseas voters by mid-September. Significant changes to rules would require them to retrain workers, buy supplies, redesign ballot envelopes and modify their voting procedures.

“Trump is sowing seeds of confusion into our election system,” said Rebekah Caruthers, chief executive of the Fair Elections Center, a nonprofit group focused on voting rights. “It’s confusing to young people, especially college students, who oftentimes are voting for the very first time.”