Allies of former President Trump are trying to maximize public opposition to the border deal "to make Senate leadership sweat," according to a source familiar with the effort.

Why it matters: Trump is once again flexing his dominance within the GOP to test whether his endorsers will break with Senate Minority Leader Mitch McConnell (R-Ky.) and Minority Whip John Thune (R-S.D.).

• Trump's team needs 41 senators to publicly oppose the bill to successfully tank it in the Senate — and they already have 20.
• They also can count on some help from Democrats: Sen. Bob Menendez (D-N.J.) called the deal "unacceptable."
• McConnell defended the deal on Monday, saying "Senate Republicans have insisted — not just for months but for years — that this urgent crisis demanded action," CNN reported.

Zoom in: The Trump allies are counting on all 31 senators who have already endorsed Trump to come out against the border bill, which also includes billions in foreign aid for Ukraine, Taiwan and Israel.

• They are hoping senators from states that Trump won handily in the last election like Sen. Mike Crapo (R-Idaho), Sen. Shelley Capito Moore (W.V.) and Cynthia Lummis (R-Wyo.) will also oppose the bill.

They expect GOP Senate leaders John Barrasso (R-Wyo.) and John Cornyn (R-Texas) to break against the bill.

• That would give cover to other members like Sen. Tim Scott (R-S.C.), a vice presidential contender, and Sen. Markwayne Mullin (R-Okla.), who comes from the same state as Sen. James Lankford, the Republican who brokered the deal.
• "This is a very bad bill for his career," Trump said Monday about Lankford. Trump endorsed Lankford in 2022 and said he was "strong on the border."

Between the lines: The policies in the package make one of the strictest bills in a century — including a massive investment in detention and deportation as well as cutting off asylum.

• But even McConnell has acknowledged to Republicans that the politics have shifted.
• Trump and other opponents don't want to give Biden a win on a critical issue in 2024.

The bottom line: The bill has virtually no chance of passing the House, but Trump's allies are trying to cast McConnell's leadership of the Senate next cycle as uncertain.

• "Don't be STUPID!!! We need a separate Border and Immigration Bill. It should not be tied to foreign aid in any way, shape, or form!" Trump said in a Truth Social post.
• "Our hope is the Senate kills this bill ... and if not, the bill will die in the House where every member of Republican leadership is united against it," Trump ally and GOP strategist Alex Bruesewitz told Axios.

Editor's note: This article has been updated to correct the spelling of Alex Bruesewitz's last name.