Sen. Mitt Romney (R-UT) announced Thursday he will join other Republican senators opposing President Donald Trump’s national emergency declaration, contending that the vote does not amount to a vote “against border security.”

Romney released a statement revealing he will vote for a resolution that would nullify Trump’s national emergency declaration and make it harder to secure the southern border. The Senate will vote on the resolution on Thursday, which President Trump has said he will veto. The House passed the bill in February.

“This is a vote for the Constitution and for the balance of powers that is at its core,” Romney said. “For the Executive Branch to override a law passed by Congress would make it the ultimate power rather than a balancing power.”

Romney continued:

This is not a vote against border security. In fact, I agree that a physical barrier is urgently needed to help ease the humanitarian crisis at the southern border, and the administration already has $4.5 billion available existing authority to fund a barrier–even without an emergency declaration. I am seriously concerned that overreach by the Executive Branch is an invitation to further expansion and future presidents. We experience a similar erosion of congressional authority with President Obama’s unilateral immigration orders– which I strenusouly opposed. In the case before us now, where Congress has enacted specific policy, to consent to an emergency declaration would be both inconsistent with my beliefs and contrary to my oath to defend the Constitution.

Romney has become the sixth Senate Republican to announce that they will vote to nullify Trump’s national emergency. He first signaled his position in January, before Trump signed a bill ending a partial government shutdown that did not contain a requested $5.7 billion for border barriers.

Sen. Mike Lee (R-UT) announced Wednesday that he, too, will vote against the national emergency after the White House declined to support his legislation that would limit a president’s national emergency authority.

Sens. Rand Paul (R-KY), Susan Collins (R-ME), Lisa Murkowski (R-AK), and Thom Tillis (R-NC) also announced that they will vote against the national emergency.

These senators have said they oppose any form of executive overreach, which includes former President Barack Obama’s Deferred Action for Childhood Arrivals (DACA) illegal alien amnesty.

However, one federal district judge ruled in August 2018 that DACA was illegal, whereas many lawyers have argued that Trump has the authority under the National Emergencies Act of 1976 to reappropriate money to build the wall.

Romney’s announcement comes as a Morning Consult/Politico poll suggests that nearly three-quarters of Republican voters would more likely vote for a candidate if they backed Trump’s national emergency on the border.

In an interview with Breitbart News this week, President Trump said he found it “hard to believe” that any Republican would vote against his efforts to secure the border.

Rep. Mo Brooks said in an exclusive interview with Breitbart News that any constitutional concern over Trump’s emergency declaration amounts to “pure, unadulterated B.S.”