Missouri Attorney General Josh Hawley is focusing on the Supreme Court in the first television ad of his Senate campaign, a sign the upcoming confirmation debate will be central to the Republican’s bid to unseat Democratic incumbent Claire McCaskill. 

Hawley’s ad will hit the airwaves Monday, the same day President Donald Trump will announce his pick to replace Justice Anthony M. Kennedy, who announced his retirement last month. 

Kennedy was a key swing vote on issues such as abortion and same-sex marriage, but Trump’s pick could likely solidify the court’s conservative majority. The vacancy has shaken up several Senate races, particularly for Democrats like McCaskill, who are running for re-election in states the president won in 2016. (He won Missouri by 19 points.)

“The eyes of the nation are on Missouri. We decide which values control the Senate and the Supreme Court,” Hawley says directly to the camera in the 30-second ad, as he walks by large columns reminiscent of the high court. “Claire McCaskill wants liberals in charge. That’s how she votes. That’s not Missouri’s way, and it won’t be my way.”

Watch: Decoding the High Court Confirmation Process — 2 Things Trump Needs to Worry About

Hawley’s ad will run statewide on broadcast and cable networks, as well as online. His campaign declined to comment on the size of the buy and how long it would be on air. 

Hawley also highlights his experience with the Supreme Court, where he clerked for Chief Justice John G. Roberts Jr. and where he met his wife, Erin.

McCaskill did not vote for Trump’s first Supreme Court pick, Neil Gorsuch, last year, joining all members of the Senate Democratic Conference, except three from states the president won by double digits. She said at the time that she voted against Gorsuch due to his “rigid ideology that always puts the little guy under the boot of corporations.”

McCaskill told Politico last week that she was not optimistic the president would nominate someone whom she would feel comfortable supporting.

Her campaign responded to Hawley’s ad Monday morning noting that McCaskill had supported a vast majority of Trump’s judicial nominees. And the campaign attempted to shift the focus back to health care, a key issue for McCaskill, by criticizing Hawley for participating in a lawsuit led by Texas challenging parts of the Affordable Care Act.

“Josh Hawley can try to mislead Missouri voters all he wants, but that won’t change Claire’s clear record of working across the aisle to get things done for Missourians,” McCaskill spokesman Eric Mee said in a statement.

“Hawley talks a lot about Missouri’s way of life, but his actions tell a different story. Instead of standing up for hard-working Missourians, Hawley is actively working to strip protections for people with pre-existing conditions, and he supports the tariffs that are slamming Missouri farmers and manufacturers,” Mee said.

The two-term senator has already been on the airwaves with two TV ads: the first featuring her work helping a World War II veteran who was the subject of government mustard gas experiments, and the second highlighting her town hall meetings throughout the state.

Inside Elections with Nathan L. Gonzales rates the Missouri Senate race a Toss-up.