North Carolina Sen. Thom Tillis says he'll vote to block President Donald Trump's emergency declaration at the border with Mexico, becoming the second Senate Republican to do so.

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In an opinion column posted late Monday by The Washington Post, Tills says he agrees with Trump that there is a crisis at the border. But he says that as a senator, he has "grave concerns" about letting a president weaken Congress' power of the purse.    

READ | FULL Thom Tillis article here

Tillis said Congress must defend its power of the purse and warned that a future Democratic president might abuse the power to advance "radical policies." 

Tillis noted that Republicans complained when former President Barack Obama used executive powers to protect some immigrants in the U.S. illegally. 

"There is no intellectual honesty in now turning around and arguing that there's an imaginary asterisk attached to executive overreach — that it's acceptable for my party but not thy party," he wrote. He said that as a conservative, "I cannot endorse a precedent that I know future left-wing presidents will exploit to advance radical policies that will erode economic and individual freedoms," such as restrictions on polluters, banks and guns.

The declaration would give Trump access to billions of dollars more than Congress approved to build his proposed wall.

Tillis faces a potentially competitive re-election next year. 

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Sen. Lisa Murkowski, R-Alaska, who doesn't face the voters until 2022, has said she is likely to oppose Trump's emergency declaration.

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