Senators unveiled a resolution on Thursday to block President TrumpDonald John TrumpUSAID administrator tests positive for COVID-19 Kamala Harris, Stacey Abrams among nominees for Time magazine's 2020 Person of the Year DOJ appeals ruling preventing it from replacing Trump in E. Jean Carroll defamation lawsuit MORE's emergency declaration to construct the U.S.-Mexico border wall.

Sens. Tom UdallThomas (Tom) Stewart UdallFormer Sen. Carol Moseley Braun stumps for Interior post: 'A natural fit for me' Five House Democrats who could join Biden Cabinet Overnight Energy: Biden names John Kerry as 'climate czar' | GM reverses on Trump, exits suit challenging California's tougher emissions standards | United Nations agency says greenhouse gas emissions accumulating despite lockdown decline MORE (D-N.M.) and Susan CollinsSusan Margaret CollinsTwo more parting shots from Trump aimed squarely at disabled workers Trump transition order follows chorus of GOP criticism The Memo: Trump election loss roils right MORE (R-Maine) introduced the resolution on the Senate floor, where it's expected to be taken up within a matter of weeks.

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The two senators, in back-to-back speeches, stressed that the Senate's vote wasn't about whether a senator supported the U.S.-Mexico border wall or Trump but about maintaining a separation of power between the executive and legislative branches on funding the government.

“I support, strongly support, protecting the institutional prerogatives of the United States Senate and the system of checks and balances that is central to the structure of our government,” Collins said. 

Udall added that the debate over the emergency declaration was about the “strength of the rule of law.”

"This is about protecting the very heart of our American system of government. ... Congress and only Congress holds the power of the purse,” he said.

The Senate resolution, which is also being co-sponsored by Sens. Lisa MurkowskiLisa Ann MurkowskiTrump administration denies permit for controversial Pebble Mine Trump transition order follows chorus of GOP criticism The Memo: Trump election loss roils right MORE (R-Alaska) and Jeanne ShaheenCynthia (Jeanne) Jeanne ShaheenTop Democrat calls Trump's Afghan drawdown 'the right policy decision' as others warn of 'mistake' Overnight Defense: How members of the Armed Services committees fared in Tuesday's elections | Military ballots among those uncounted in too-close-to-call presidential race | Ninth US service member killed by COVID-19 Biden wins New Hampshire MORE (D-N.H.), comes two days after the House passed its measure to block Trump’s emergency declaration.

All Democrats are expected to back the resolution once it comes to the Senate floor. They’ll need four Republican senators to get it to Trump’s desk, where he’s said he will veto it.

So far, three Republican senators have said they will vote for the resolution: Collins, Murkowski and Thom TillisThomas (Thom) Roland TillisNorth Carolina — still purple but up for grabs Team Trump offering 'fire hose' of conspiracy Kool-Aid for supporters Loeffler isolating after possible COVID-19 infection MORE (N.C.).

Several other Republicans have voiced concerns about Trump’s emergency declaration.