Former President Trump is taking on Senate GOP Leader Mitch McConnell (R-Ky.) and his leadership team by calling on Republican lawmakers to reject a compromise on border security.

The runaway front-runner for the GOP presidential nomination is also setting up a crucial battle over both his party’s future and Ukraine, as precious aid to that country is tied to the border deal along with help for Israel and the Indo-Pacific.

Trump has said Republicans should say “no” to any deal that falls short of “everything needed” to stop the flow of migrants, a message that pointedly puts pressure on new Speaker Mike Johnson (R-La.) to walk the line. Johnson has been under pressure from the Senate GOP and the White House to agree to an emerging Senate deal.

Members of McConnell’s leadership team immediately pushed back against what appeared to be an attempt by Trump to tank the Senate deal.  

“It’s not helpful,” said Senate Republican Whip John Thune (S.D.), the No. 2-ranking Senate GOP leader.  

Thune argued the Senate’s Ukraine package is the best chance Republicans have to staunch the flow of migrants, which exceeded more than 300,000 people in December alone — an all-time monthly high.