The Senate is scheduled to vote Thursday on a resolution blocking President Donald Trump's emergency declaration.
Senate Majority Leader Mitch McConnell's already said he expects the upper chamber to pass the measure. Republican Sens.
Rand Paul, Susan Collins, Lisa Murkowski and Thom Tillis said they will vote in favor of the resolution, which passed the House last month.
Assuming all Democratic senators support the resolution, those four Republicans would provide the simple majority needed to send it to President Trump's desk.
But the president has said he'll "100 percent" veto the resolution.
And McConnell told reporters he doesn't think lawmakers have the two-thirds majority needed in each chamber to override that veto.
President Trump issued the national emergency declaration in February.
It allows him access to certain government funding to pay for a U.S.-Mexico border wall without going through Congress. Additional reporting from Newsy affiliate CNN .