President Trump targeted Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D-Mo.) in a tweet on Sunday, predicting a Republican candidate will take her Senate seat in 2018.

"I will also be going to a wonderful state, Missouri, that I won by a lot in '16. Dem C.M. is opposed to big tax cuts. Republican will win S!" the president said.

I will also be going to a wonderful state, Missouri, that I won by a lot in '16. Dem C.M. is opposed to big tax cuts. Republican will win S! — Donald J. Trump (@realDonaldTrump) August 27, 2017

McCaskill is seeking a third Senate term.

But Missouri, which Trump won by 19 points in November, is seen as a potential pick up for Republicans in 2018.

Democrats lost Missouri’s 2016 Senate race, with incumbent Sen. Roy Blunt Roy Dean BluntThis week: Supreme Court fight over Ginsburg's seat upends Congress's agenda McConnell locks down key GOP votes in Supreme Court fight Murkowski: Supreme Court nominee should not be taken up before election MORE (R) holding off a challenge from the Democratic nominee, Jason Kander.

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The state's Republicans now appear to be rallying around Missouri Attorney General Josh Hawley (R).

Politico reported that the conservative Club for Growth has raised $10 million to support Hawley's Senate bid.

McCaskill, however, is likely to put up a strong fight, having already raised more than any other vulnerable Democratic incumbent in the second quarter of 2017.