The Denver Post published an op-ed Thursday declaring it “was a mistake” for them to endorse Sen. Cory Gardner -- hours after the Colorado lawmaker sided with President Trump's border security declaration rather than joining 12 fellow Republicans in voting against it.

The newspaper wrote it endorsed the Republican senator in 2014 “because we believed he’d be a statesman.”

“We knew he’d be a conservative voice in Congress, to be certain, but we thought his voice would bring ‘fresh leadership, energy and ideas,’” the op-ed read.

However, the paper said Gardner “has been too busy walking a political tight rope to be a leader.”

“We no longer know what principles guide the senator and regret giving him our support in a close race against Mark Udall,” the op-ed said.

REPUBLICANS WHO VOTED AGAINST TRUMP’S BORDER EMERGENCY DECLARATION

The Denver Post noted Gardner did not join the 12 Republicans who, with Senate Democrats, voted 59-41 to block Trump's national emergency declaration. Such a declaration would allow the president to move government money to fund a wall across the U.S.-Mexico border. The Senate Republicans who voted against the declaration included Sen. Mike Lee of Utah, Sen. Susan Collins of Maine, and Sen. Rand Paul of Kentucky.

The paper noted that they did “expect to disagree with our lawmakers from time to time” but “these were extraordinary times.”

“This is a bogus emergency that takes executive over-reach to an extreme not seen even under President Barack Obama,” the op-ed stated. “Trump’s declaration is an abuse of his power, a direct overturning of Congress’ deliberate decision to pass a federal budget without funding for a wall.”

The Post said it was “surprised by Gardner’s vote” and called it “inconsistent with every stance he has taken on Trump’s presidency.”

Gardner released a statement Thursday explaining his vote.

SENATE VOTES TO BLOCK TRUMP’S BORDER EMERGENCY DECLARATION, IN BIPARTISAN REBUKE TEEING UP VETO

"There is a crisis at the border and Nancy Pelosi and Chuck Schumer have prevented a solution. As a result, the president has declared a national immigration emergency, legal authority which he clearly has under the 1976 law, a law invoked 56 times by every previous president since Jimmy Carter. Between October and February, border patrol apprehensions were up nearly 100 percent and since 2012, border patrol methamphetamine seizures are up 280 percent. It should never have come to this, but in the absence of Congressional action, the president did what Nancy Pelosi and Chuck Schumer refused to do," Gardner’s statement read.

The Post asked why Gardner didn’t lobby with his “fellow Republicans to pass a budget in December prior to the shutdown that included Trump’s requested $5.7 billion for a wall?”

“In Gardner’s defense, he said he voted to open the government because he opposes shutdowns as a matter of principle, a position we lauded him for at the time. But we’re surprised he doesn’t feel the same twinge of principle when it comes to an executive order that is so blatantly a repudiation of Congress’ will,” the Denver Post wrote.

The paper said the lawmaker “could still prove to be a great senator for Colorado” who puts his state above party -- something the paper said is “rare” these days.

Gardner is expected to face a competitive race when he is up for reelection next year. He recently endorsed Trump’s reelection despite opposing Trump during the 2016 GOP primary. Later, he endorsed Trump but rescinded it following the “Access Hollywood” tape.

The Associated Press contributed to this report.