FILE – Sen. Ted Cruz, R-Texas, questions Supreme Court nominee Ketanji Brown Jackson during a Senate Judiciary Committee confirmation hearing on Capitol Hill in Washington, March 23, 2022. Texas Sen. Ted Cruz is endorsing former state treasurer Josh Mandel in the heated Republican primary for Ohio’s open U.S. Senate seat. Cruz’s move could be particularly valuable among conservative voters in the absence of an endorsement in the race by Donald Trump, who has yet to weigh in despite candidates working hard to woo him — and he may not. (AP Photo/Alex Brandon, File)

COLUMBUS, Ohio (AP) — Texas Sen. Ted Cruz endorsed former Ohio Treasurer Josh Mandel on Monday in the heated Republican primary for an open U.S. Senate seat, a potentially critical campaign boost just as early voting is set to begin in the Midwestern battleground.

Cruz’s decision could be particularly valuable among conservative voters in the absence of an endorsement in the race by Donald Trump, who has yet to weigh in despite candidates working hard to woo him — and he may not.

Cruz, who sought the GOP presidential nomination in 2016 that Trump won and may run again in 2024, is one of the highest-profile Republicans in the Senate. He and Mandel share an affinity for trying to exploit cultural divisions for political gain.

Polling shows Cleveland investment banker Mike Gibbons slightly edging Mandel at the top of the crowded GOP field vying to replace retiring Republican Sen. Rob Portman. Also running in the May 3 primary are former state Republican chair Jane Timken, author and venture capitalist J.D. Vance, state Sen. Matt Dolan and entrepreneurs Mark Pukita and Neil Patel.

FILE – Josh Mandel, a Republican former Ohio treasurer running for an open U.S. Senate seat in Ohio, speaks during a debate against Morgan Harper, a progressive Democrat, Jan. 27, 2022, in Columbus, Ohio. Texas Sen. Ted Cruz is endorsing former state treasurer Josh Mandel in the heated Republican primary for Ohio’s open U.S. Senate seat. Cruz’s move could be particularly valuable among conservative voters in the absence of an endorsement in the race by Donald Trump, who has yet to weigh in despite candidates working hard to woo him — and he may not. (AP Photo/Jay LaPrete, File)

Early voting begins Tuesday.

In a statement to The Associated Press, Cruz said he chose Mandel because he will stand up to “radical democrats” who want to exploit crises facing the nation “to deliver socialism to America.”

“A United States Marine, Josh is a proven fighter for our American way of life, a champion for the unborn, and a stalwart advocate for our religious liberties,” Cruz said.

In an interview, Mandel said that if he is elected, he looks forward to “being reinforcements for conservative fighters like Ted Cruz.”

“As we’ve seen in his 10 years in the Senate, he takes on squishy establishment Republicans just as fast as he takes on leftist Democrats,” Mandel said. “Because for Ted, and for me, this is not about (a) Republican vs. Democrat, shirts vs. skins type game. This is about standing up for the Constitution, for traditional American values, and saving the country for our kids and grandkids.”

Cruz has made a series of endorsements in this year’s primaries as he looks to the future. For the Senate, he is backing businessman David McCormick in Pennsylvania and Missouri Attorney General Eric Schmitt.

The conservative group Club for Growth helped elect Cruz in 2012 in a competitive race and it’s working this year to put Mandel in office. President David McIntosh said the group’s polling shows Gibbons and Mandel neck and neck.

“One of the things we’ve seen is, probably second to Trump, an endorsement from Ted Cruz signals the person he’s endorsing is a true believer and a fighter for the things they believe in,” he said.

Mandel has also been endorsed by North Carolina Rep. Madison Cawthorn, who has received criticism from a larger swath of Republicans for recent comments, including one in which he called Ukrainian President Volodymyr Zelenskyy a “thug.” Utah Sen. Mike Lee, a conservative ally of Cruz, is also supporting Mandel.

Vance has the backing of Missouri Sen. Josh Hawley and Reps. Jim Banks of Indiana and Marjorie Taylor Greene of Georgia. Gibbons has the support of Kentucky Sen. Rand Paul.

Portman endorsed Timken in February, as did former Trump adviser Kellyanne Conway. Timken also has the support of Sens. Shelley Moore Capito of West Virginia, Joni Ernst of Iowa and Deb Fischer of Nebraska.