Sen. Lamar Alexander Andrew (Lamar) Lamar AlexanderGraham: GOP has votes to confirm Trump's Supreme Court nominee before the election The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy This week: Supreme Court fight over Ginsburg's seat upends Congress's agenda MORE (R-Tenn.) said on Thursday that he would vote for a resolution blocking President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE’s emergency declaration.

Alexander, asked how he would vote after a floor speech criticizing Trump, said he would vote for the resolution of disapproval that is coming up for a vote later Thursday.

Alexander has voiced concerns for weeks about Trump's actions, but remained tightlipped as recently as earlier Thursday about how he would vote. He reiterated his concerns during a floor speech shortly before he confirmed to reporters that he would vote for the resolution of disapproval.

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"The president's emergency declaration to take an additional $3.6 billion that Congress has appropriated for military hospitals, for basics and for schools … is inconsistent with the United States Constitution that I took an oath to support and defend," Alexander said from the Senate floor.

Alexander is the seventh Republican senator to announce they would vote for the resolution of disapproval, which Trump is pledging to veto.

“This declaration is a dangerous precedent. Already, Democrat presidential candidates are saying they would declare emergencies to tear down the existing border wall, take away guns, stop oil exports, shut down offshore drilling and other left-wing enterprises — all without the approval of Congress," he said.

Alexander, an institutionalist viewed as a member of the GOP governing wing, is retiring at the end of the current Congress, giving him the freedom to vote against Trump without having to worry about political blowback.

He is the second GOP senator to come out in support of blocking Trump's emergency declaration on Tuesday.

In addition to Alexander, GOP Sens. Susan Collins Susan Margaret CollinsSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (Maine), Mike Lee Michael (Mike) Shumway LeeMcConnell shores up GOP support for coronavirus package McConnell tries to unify GOP Davis: The Hall of Shame for GOP senators who remain silent on Donald Trump MORE (Utah), Lisa Murkowski Lisa Ann MurkowskiSenate GOP aims to confirm Trump court pick by Oct. 29: report Senate GOP sees early Supreme Court vote as political booster shot Pence defends Trump's 'obligation' to nominate new Supreme Court justice MORE (Alaska), Rand Paul Randal (Rand) Howard PaulSecond GOP senator to quarantine after exposure to coronavirus GOP senator to quarantine after coronavirus exposure The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE (Ky.), Mitt Romney Willard (Mitt) Mitt RomneySenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (Utah) and Thom Tillis Thomas (Thom) Roland TillisThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting OVERNIGHT ENERGY: EPA head questions connection of climate change to natural disasters | Pebble Mine executives eye future expansion in recorded conversations | EPA questions science linking widely used pesticide to brain damage in children Liberal super PAC launches ads targeting vulnerable GOP senators over SCOTUS fight MORE (N.C.) have said they will support the resolution of disapproval.

The Senate is expected to pass the resolution of disapproval later Thursday, sparking the first veto showdown with Trump, who is adamantly opposed to the resolution.

Trump made a series of eleventh-hour pleas to Republicans to vote against the resolution of disapproval, ranging from being open to amending emergency powers in the future to warning they were siding with Speaker Nancy Pelosi Nancy PelosiPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare House lawmakers reach deal to avert shutdown Centrist Democrats 'strongly considering' discharge petition on GOP PPP bill MORE (D-Calif.).

"Prominent legal scholars agree that our actions to address the National Emergency at the Southern Border and to protect the American people are both CONSTITUTIONAL and EXPRESSLY authorized by Congress," Trump said in a tweet Thursday morning.

He pivoted in a subsequent post, adding: "A vote for today’s resolution by Republican Senators is a vote for Nancy Pelosi, Crime, and the Open Border Democrats!"