President Donald Trump told senators on Wednesday to use their discretion but also warned them that voting to block his national emergency declaration would be a bad move.

“This is not a vote on constitutionality because it is constitutional — it’s not a vote on precedent,” Trump said to reporters during a policy meeting on drug trafficking.

“This is a vote on border security and it’s a vote on drugs trafficking and all of that. I think most Republicans senators fully understand that.”

Last month, Trump declared a state of emergency along the southern border amid a contentious political fight. He signed a compromise deal that failed to meet his border wall requests while also making the emergency declaration.

Trump declared the emergency to help secure millions of dollars for the construction of a border wall. Democrats quickly moved to oppose the decision with a resolution that would block it.

The House passed it on February 26; the Senate could pass it as well, as there are enough lawmakers apparently crossing party lines ahead of a vote Thursday. Trump has said he would veto the resolution.

Related: House Dems Pass Resolution to Block Trump’s Border Emergency

“I said use your own discretion,” Trump told the media on Thursday. “But I think it’s a bad vote if they go against [it]. I think anyone going against border security, drug trafficking, human trafficking — that’s a bad vote. Democrats are for open borders. They’re for crime, frankly — they are for crime.”

Rep. Joaquin Castro (D-Texas) introduced the resolution soon after the president declared the emergency.

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“I guess they think it’s good politically. I think it happens to be bad politically,” Trump said. “The Democrats, in order to make things more difficult, they are for open borders and they are for crime and the Republicans aren’t. But I told Republican senators to vote any way they want. Vote how you feel good.”

Sen. Rand Paul (R-Ky.) became the fourth Republican senator on March 4 to express his support for the resolution. Senate Democrats only need four senators to break party lines in order to get it passed.

Senate Majority Leader Mitch McConnell (R-Ky.) said in response that he expects the resolution to pass.

Related: Dems Introduce Resolution to Block Trump’s Emergency Declaration

Trump is among the numerous presidents who have used the National Emergencies Act (NEA) since it was passed back in 1976. Trump has repeatedly argued the situation at the southern border is a crisis severe enough to warrant such a dramatic move.

He is potentially freeing up billions of dollars in emergency funds for the construction of the border wall.

Senate Republicans are also considering a bill that would restrict future emergency declarations.

Sen. Mike Lee (R-Utah) introduced it; it would automatically end all future emergency declarations after 30 days unless they get congressional approval.

Congress currently can cancel an emergency declaration but only by passing a resolution that could overcome a veto.

McConnell said in response to the bill that nearly everyone in his caucus agrees with the president about securing the border. But he admitted there is concern about the emergency declaration.

McConnell also stressed his caucus believes the president did nothing wrong under current law but that the law itself might need to change.

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