Ohio state treasurer Josh Mandel upended his state's political landscape on Friday when he told his supporters in an email that he would no longer run against Democratic Sen. Sherrod Brown in November's election. The announcement came as an abrupt blow to the GOP as Mandel was seen as the likely nominee.

Mandel had already challenged Brown in a close 2012 race and was regarded by both parties as a strong candidate this year. Democrats had feared Brown would be a prime target since he defeated Mandel by 6 points in their earlier contest while Donald Trump had pulled off an 8-point margin in Ohio in 2016, meaning that the state might be more open to a Republican without the corporate executive profile of the GOP's 2012 nominee, Mitt Romney. Aside from Brown, Ohio voters have generally preferred Republican statewide officials in recent elections even though they did vote for Barack Obama during his two presidential campaigns.

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In his message to supporters, Mandel said that his wife, Ilana, had a medical condition which required such extensive treatment that he could not be absent at home for the amount of time required to run a successful Senate campaign.

Thus far, the only other official candidate in the GOP primary is Michael Gibbons, a banker from Cleveland who had attracted little popular support before Mandel's announcement. On Friday, Politico reported that Rep. Jim Renacci, who had been running for the Ohio governor's office, is now leaning toward getting into the Senate race instead.

Whoever decides to jump in will have to move quickly. The Ohio deadline for candidates is Feb. 7.