With only a month to go until the midterm elections, Senator Claire McCaskill of Missouri is beginning to fall behind her Republican challenger, Josh Hawley, according to a new poll.

The poll, which shows Hawley leading McCaskill 52 percent to 44 percent, was commissioned by the pro-Hawley PAC Missouri Rising Action. But it suggests Hawley has gained ground since June, when Rising Action’s previous poll had him trailing McCaskill 46 percent to 42 percent.

Conducted between September 29 and October 2, the poll comes at the climax of the Senate’s messy fight over the nomination of Supreme Court nominee Brett Kavanaugh, who became even more controversial last month after accusations of decades-ago sexual assault were made public. McCaskill is not on the Judiciary Committee, the site of most of the pitched battles over Kavanaugh, but she announced last month that she would vote against confirmation based on his presumed opposition to campaign finance reform.

“It is his allegiance to the position that unlimited donations and dark anonymous money, from even foreign interests, should be allowed to swamp the voices of individuals that has been the deciding factor in my decision to vote no on his nomination,” McCaskill said in a statement on September 19.

Meanwhile, Hawley has been hammering McCaskill relentlessly in speeches and TV ads for her approach to Supreme Court nominees practically since Justice Anthony Kennedy announced his retirement in July—and has ratcheted up the pressure still further since the confirmation proceedings became the all-consuming political controversy of the last month.

“The Constitution gives the U.S. Senate the responsibility of confirming justices to the Supreme Court,” Hawley says in an ad released by his campaign Wednesday. “But the people in our Senate today? They’ve created a circus. Liberals like Claire McCaskill and Chuck Schumer, they don’t want the truth. They only want power, and too many Republicans won’t stand up.”

According to most nonpartisan polling, the race remains close. The current RealClearPolitics polling average shows Hawley with a 0.4 percent lead, with two September polls showing a Hawley lead, one giving McCaskill the edge, and three others showing a statistical tie.