CLEVELAND, Oho - Republican Ohio Treasurer Josh Mandel announced Friday his withdrawal from the race for U.S. Senate.

Mandel, largely considered the Republican frontrunner, cited an unspecified health issue with his wife, Ilana, as the primary reason.

"After recent discussions with our family and healthcare professionals, it has become clear to us that it's no longer possible for me to be away from home and on the campaign trail for the time needed to run a US Senate race," Mandel said in a written statement. "Therefore, I'm writing today to let you know that I am ending my campaign for US Senate in order to be there for my wife and our three children."

Mandel will finish his term as treasurer that ends in 2018.

Mandel was vying to challenge U.S. Sen. Sherrod Brown, a Democrat, in a rematch of the 2012 race. His abrupt departure leaves Republicans scrambling just a little more than a month before the filing deadline in a race that many national observers think could be hotly contested. Republican President Donald Trump won the state by 8 points.

Ohio Republican Party Chairman Jane Timken said Friday that the party would continue to focus on electing Republicans while offering condolences to Mandel.

"Josh Mandel has made an honorable decision to be with his family in a time of need," Timken said. "While we are saddened to see him leave the race, we understand, and offer our thoughts and prayers to his family."

Justin Barasky, Brown's campaign manager, also offered sympathy to the Mandel family.

"At this time, we wish Josh, Ilana and their family the best of health," Barasky said. "We hope for Ilana's full and speedy recovery."

Mandel, originally from Lyndhurst, was first elected statewide in 2010 as treasurer. He challenged Brown for the Senate in 2012, losing by six percentage points, and won reelection in 2014 to his treasurer's spot.

Mandel's announcement was a shocker around the state, catching GOP operatives, insiders and elected officials completely off guard.

"Josh Mandel was the GOP heavyweight frontrunner in this race," said Nick Everhart, a Republican operative in Ohio. "For him to be out changes everything, and opens up an opportunity for a lot of people, who passed to avoid what looked like a futile uphill primary fight."

Who that could be is up in the air.

Mandel's most serious challenger so far has been Cleveland businessman Mike Gibbons, who has garnered serious endorsements in recent weeks, including from the Franklin County Republican Party.

Gibbons offered prayers to Mandel's wife and said it was time for the party to come together in the race.

"Now is the time for Republicans to unite as one so we can defeat Sherrod Brown," Gibbons said.

Despite some recent successes, Gibbons is not well known around the state, leaving an opening for a number of potential challengers. He committed $5 million of his own money to the campaign today, having already loaned himself $570,349.

An aide to Gov. John Kasich, who is term limited, said the governor is not interested in running.

Rob Nichols, a spokesman for U.S. Rep. Pat Tiberi who considered a run against Mandel, said Tiberi also is not eying the seat.

"The congressman's decision in May not to pursue a Senate run had nothing to do with Josh Mandel, and the congressman looks forward to starting his new role with the Ohio Business Roundtable come January 16," Nichols said.

Two possible candidates are currently in the race for governor. U.S. Rep. Jim Renacci of Wadsworth or Lt. Gov. Mary Taylor could look at running for Senate after Attorney General Mike DeWine and Secretary of State Jon Husted, the GOP frontrunners for governor, announced they would join a single ticket.

A spokesman for Renacci said he hadn't spoken with the congressman about it and declined to comment.

Taylor's campaign said she was receiving calls about running, but hadn't made a decision yet.

JD Vance, author of Hillbilly Elegy, also expressed interest in the Senate race earlier in the year before declining to run. A source familiar with Vance said he would likely take another look at the seat.

U.S. Reps. Bill Johnson of Marietta and Jim Jordan from Champaign County are two other options. Johnson is a conservative ally of Trump while Jordan is a founding member of the far-right Freedom Caucus.

A spokesman for Johnson declined to rule out a run, but Johnson said in a statement he was focused on his current House term.

"Over the last few years, many people have encouraged me to run for Senate but I'm focused right now on two things: representing those I serve in Eastern and Southeastern Ohio, and running for the House Budget Committee chairmanship, which will be decided next Tuesday evening," Johnson said.

Jordan's spokeswoman also wouldn't address whether Jordan might seek the seat, instead releasing a statement that called Mandel "a great conservative fighter and family man."

"I'm disappointed that Ohioans won't have the opportunity to vote for him, but he is making the right decision for his wife and kids," Jordan's statement said. "Our thoughts and prayers are with Ilana and the entire Mandel family."

Spokespeople for U.S. Reps. Dave Joyce, Bob Gibbs and Bob Latta said they all were not interested in running.

One other possibility might be State Sen. Matt Dolan, who has name recognition and a record as a moderate.

A Washington Republican knowledgeable about Ohio politics and the Senate race said "there will be a lot of discussions" on the race "in the next five or six days."

Cleveland.com's Washington Bureau Chief Steve Koff, Washington reporter Sabrina Eaton, Columbus reporter Jeremy Pelzer and political reporter Andrew Tobias contributed reporting.