Sen.(S.D.), the No. 2 Republican in the Senate, on Tuesday appeared to warn thatcould fail to prevent a handful of Republicans from voting with Democrats to block a national emergency declaration to construct a wall on the U.S.-Mexico border.

ADVERTISEMENT

"[But] the concern I guess I would have is that on the front end that vote, based on the concerns that a lot of our members have expressed, that it might be a, you know, a tough vote to win here in the Senate," Thune said.

He added that when Trump moves forward he needs to have a "clear-eyed understanding of kind of what the state of play is up here and of the concerns that our members have, both with respect to the precedent and the constitutionality."

Trump has refused to rule out issuing a national emergency declaration to build a border wall if Congress can't reach a deal on border security by Feb. 15 to prevent another partial government shutdown.

If Trump declares a national emergency, Democrats would be able to force a vote on a resolution to try to block him. That vote would need only a simple majority to pass.

Thune told reporters that if a resolution of disapproval initially passes the Senate with less than 67 votes, the amount needed to override a veto, Trump "would win it on the back side.""We don't know what route the president's going to take, so I'm not going to speculate on it at this point," McConnell said . "I'm going to withhold judgement about that until we see what he does."