Top Republican Senate recruit Josh Hawley is taking concrete steps to run for Senate in 2018 with the opening of an exploratory committee, sources close to him told the Washington Examiner on Thursday.

Hawley, the Missouri attorney general, was to file his federal exploratory committee papers on Friday with his state campaign committee in the process of informing donors that it would no longer accept contributions. He plans to begin raising money aggressively, according to sources close to Hawley.

Hawley's move toward a Senate run was sure to cheer Senate Majority Leader Mitch McConnell, R-Ky., and the team at the National Republican Senatorial Committee, the Senate GOP campaign arm.

They have been without a top candidate to challenge vulnerable Democratic Sen. Claire McCaskill since Rep. Ann Wagner, R-Mo., decided against a Senate bid in favor of running for re-election to the House.

McCaskill was equally endangered in 2012 but won re-election in part because the Republicans nominated a flawed challenger.

Hawley running would appear to quell GOP concerns of a repeat. He's a candidate who can unify the conservative and establishment wings of the party and has the support of top Republican donors in Missouri.

His entrance into the race had been taking longer than some insiders expected while he discussed the matter with family and close advisors.