Rep. Ann Wagner has opted against a 2018 Senate bid, choosing re-election to the House over challenging vulnerable Democratic Sen. Claire McCaskill.

Wagner's surprise move, finalized over the weekend, is a blow to the Republican Party. She was the leadership's prized Senate recruit in Missouri and viewed as the answer to McCaskill, endangered but scrappy.

McCaskill was in bad political shape five years ago but survived anyway because the GOP nominee, then-Rep. Todd Akin, was so poorly received, particularly among female voters. McCaskill might have caught another break.

In a statement provided to the Washington Examiner Monday, Wagner said the decision came after many conversations with her husband and children.

"Those who know me well know I put my family and my community first. While I am grateful for the incredible support and encouragement I have received from across Missouri to run for United States Senate, I am announcing today my intention to run for re-election to the United States House of Representatives in 2018," she said.

Wagner holds two plum committee assignments — subcommittee chairwoman of Oversight and Investigations on the House Financial Services Committee and she also sits on the House Foreign Affairs Committee.

"The 2nd District is my home. It's where I grew up, went to school, have worked and volunteered, raised my kids, and attend church every week – there is no greater honor than representing a place and people that I love," Wagner added.

Republicans close to the congresswoman stressed that the decision had little, if anything, to do with the politics of giving up her relatively safe seat to run for Senate with an unpopular Republican in the White House and a healthcare agenda that has been rejected by a broad cross-section of Americans.

Democrats lead Republicans by 8 percentage points, 47.2 percent to 39.2 percent, in the latest polling average of surveys measuring voters' generic ballot preferences for Congress. The GOP's House and Senate healthcare bills are both under water in recent polling.

Wagner had the support of Senate Majority Leader Mitch McConnell and the National Republican Senatorial Committee, the party's Senate campaign arm, and she has a good relationship with the White House despite her strong connections to the Bush family.

The congresswoman has raised money at a decent clip under the assumption that she would announce for Senate this year and is poised to report another quarter similar to her first quarter, when she raised more than $804,000.

Trump's approval ratings are solid in Missouri, bucking national trends that have seen his numbers hover around 40 percent.

The president's exotic Twitter habit, ongoing war with the media, chaotic governing style and the uncertain prospects for his agenda on Capitol Hill are not necessarily a drag on the down ticket in Missouri during the midterm elections as it might be in a swing state.

Trump shellacked Democrat Hillary Clinton in November in Missouri, winning the state with 57 percent of the vote.

Senate Democrats are under threat in several red states where their incumbents are running for re-election and could lose seats in 2018. But with Trump's recent controversies, they're likely to take solace in Wagner's decision and hype it as a rebuke of the president.