President Trump on Wednesday endorsed Mike Lindell, the chief executive of MyPillow, in a bid to be governor of Minnesota, throwing his support behind a candidate best known for promoting the falsehood that voting machines in the United States are often rigged and have flipped elections.

Mr. Trump called Mr. Lindell “one of America’s greatest and most hard working Patriots” in a post on his social media site. Mr. Trump, who has regularly criticized Minnesota’s Democratic leaders, citing a fraud scandal and the state’s immigration policies, said that Mr. Lindell could bring the state back “from oblivion and embarrassment.”

The endorsement jolted a race that has been upended by the president’s focus on the state. After the Trump administration began an immigration crackdown in the state while railing against fraud in social services programs, Gov. Tim Walz, a Democrat, abandoned his bid for a third term late last year.

Senator Amy Klobuchar, a popular Democrat with a history of winning by double-digit margins, announced a bid early this year and is seen as a formidable opponent in a state that hasn’t elected a Republican to statewide office in two decades.

Mr. Lindell, who has promised to cut taxes and work with federal officials on immigration enforcement, faces two main rivals in a Republican primary next month: Kendall Qualls, a businessman who won the endorsement of the state Republican Party, and Lisa Demuth, the speaker of the Minnesota House of Representatives.

A poll conducted by the Minnesota Star Tribune in June showed that Ms. Klobuchar had a commanding lead over Mr. Lindell.

Mr. Lindell has been among the most vocal figures sowing doubt about the reliability of voting machines and was an outspoken supporter of Tina Peters, a county clerk in Colorado who was convicted of tampering with voting machines in a failed attempt to show that they had been used to rig the 2020 election. Last year, a jury in Denver found that Mr. Lindell had defamed a former employee of Dominion Voting Systems, a manufacturer of voting machines, and ordered him to pay $2.3 million in damages.

Mr. Lindell, a Minnesota native, has started several businesses, including a pillow manufacturing firm and a media corporation.

In this primary season, Mr. Trump has had a mixed record of success with candidates he has endorsed. Candidates for governor he backed in Iowa and Georgia lost their races, while the candidates he endorsed in Alabama, California and Ohio prevailed.

Ruth Igielnik contributed reporting.