Americans For Prosperity (AFP), a libertarian-conservative group funded by billionaire Charles Koch, is spending $1 million on advertisements to support vulnerable Republican senators in 2020. Sens. John Cornyn, R-Texas, Steve Daines, R-Mt., David Perdue, R-Ga., and Thom Tillis, R-N.C., all face challenging reelection races in November.

“Americans are resilient and capable of extraordinary things. As individuals and businesses across our country begin to rebuild and recover, we know that we can count on John Cornyn, Steve Daines, David Perdue, and Thom Tillis to continue their work to promote opportunity for all Americans,” AFP Action senior advisor Tim Phillips told The Hill.

Cornyn has only 37% approval and 36% disapproval, according to a Quinnipiac Poll released on June 3. Cornyn’s Democratic opponent will be determined next month and his race comes after Sen. Ted Cruz earned a tight victory in 2018 against Democrat Robert "Beto" O'Rourke. Cornyn has strongly supported Trump and voted to acquit him in the Senate impeachment trial in February.

Daines faces a tough race against Gov. Steve Bullock, who sought the Democratic nomination for president. A recent poll from Montana State University shows Bullock with 46% support to Daines’ 39% support.

Perdue will be running against Democrat Jon Ossoff. Perdue has been called a “caricature of Washington corruption,” by Ossoff. According to FiveThirtyEight, Perdue has voted with Trump’s position 94.7% of the time. Perdue’s support for Trump could be a liability in the fall, as Trump's approval rating has fallen amid the coronavirus and the George Floyd protests.

Tillis will be facing off against Democrat Cal Cunningham in the fall. A poll from PPP earlier this month put Cunningham at 43% support to Tillis’ 41%.

Koch has a net worth of $47.6 billion and is the CEO and Chairman of Koch Industries. The Wichita, Kansas-based company is involved in sectors such as minerals, refining, commodity trading and consumer products.