Top Republican recruit U.S. Rep. Ann Wagner of Missouri says she's not running for Democratic U.S. Sen. Claire McCaskill's seat in 2018.
Wagner said in a statement Monday that she's instead running for re-election to her suburban St. Louis House seat.
Wagner's announcement creates a vacuum for Republicans hoping to win the U.S. Senate seat. McCaskill is among 10 Senate Democrats running in 2018 in states won by President Donald Trump.
Wagner's decision not to run also may indicate that some Republicans feel the race could be tougher than expected, given Trump's low approval ratings and an energized Democratic base.
Former Sen. John Danforth was among several high-profile Republicans who previously encouraged Missouri Attorney General Josh Hawley to run.
Hawley has not yet said whether he'll run in 2018.