JEFFERSON CITY, Mo. (AP) – Missouri Republican U.S. Senate candidate Josh Hawley is traveling the state to kick off his campaign.

The attorney general will visit the Kansas City area, Springfield and St. Louis on Tuesday. He’s making a bid for the Republican nomination to challenge incumbent Democrat Sen. Claire McCaskill.

Hawley officially announced his candidacy in October, but he’s done relatively little campaigning since then. Tuesday will mark the start of more active campaigning on his part.

The stakes are high. Republicans hold a slim 51-member majority in the Senate, so the outcome of the Missouri election could determine party control of the chamber.

McCaskill is seen as one of the most vulnerable incumbents as a Democrat in a state won by President Donald Trump by nearly 20 percentage points in 2016.