Senators unveiled a resolution on Thursday to block President TrumpDonald John TrumpMost Americans break with Trump on Ukraine, but just 45 percent think he should be removed: poll Judge orders Democrats to give notice if they request Trump's NY tax returns Trump's doctor issues letter addressing 'speculation' about visit to Walter Reed MORE's emergency declaration to construct the U.S.-Mexico border wall.

Sens. Tom UdallThomas (Tom) Stewart UdallBureau of Land Management staff face relocation or resignation as agency moves west Overnight Energy: EPA watchdog slams agency chief after deputy fails to cooperate in probe | Justices wrestle with reach of Clean Water Act | Bipartisan Senate climate caucus grows Hillicon Valley: Twitter to refuse all political ads | Trump camp blasts 'very dumb' decision | Ocasio-Cortez hails move | Zuckerberg doubles down on Facebook's ad policies | GOP senator blocks sweeping election reform bill MORE (D-N.M.) and Susan CollinsSusan Margaret CollinsFeehery: Pivoting to infrastructure could help heal post-impeachment wounds Progressive group to spend as much as M to turn out young voters Overnight Defense: Erdoğan gets earful from GOP senators | Amazon to challenge Pentagon cloud contract decision in court | Lawmakers under pressure to pass benefits fix for military families 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 MurkowskiImpeachment hearings don't move needle with Senate GOP Hillicon Valley: Federal inquiry opened into Google health data deal | Facebook reports millions of post takedowns | Microsoft shakes up privacy debate | Disney plus tops 10M sign-ups in first day Senators press FDA tobacco chief on status of vaping ban MORE (R-Alaska) and Jeanne ShaheenCynthia (Jeanne) Jeanne ShaheenProgressive group to spend as much as M to turn out young voters On The Money: US paid record .1B in tariffs in September | Dems ramp up oversight of 'opportunity zones' | Judge hints at letting House lawsuit over Trump tax returns proceed Overnight Energy: EPA watchdog slams agency chief after deputy fails to cooperate in probe | Justices wrestle with reach of Clean Water Act | Bipartisan Senate climate caucus grows 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 TillisFeehery: Pivoting to infrastructure could help heal post-impeachment wounds Progressive group to spend as much as M to turn out young voters This week: House kicks off public phase of impeachment inquiry MORE (N.C.).

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