CNN  — 

Senate Majority Leader Mitch McConnell bluntly warned Democrats on Thursday against weakening the legislative filibuster, an idea that has gained momentum with some presidential candidates and not ruled out by Senate Democratic leaders who backed a similar move six years ago to make it easier to break filibusters of most presidential nominees.

“The legislative filibuster is directly downstream from our founding tradition. If that tradition frustrates the whims of those on the far left, it is their half-baked proposals and not the centuries-old wisdom that need retooling,” McConnell wrote in an op-ed for The New York Times.

The Kentucky Republican argued that “strong minority rights have always been the Senate’s distinguishing feature” and reminded Democrats that when they used the “nuclear option” in 2013 to lower the supermajority threshold to break a filibuster for nominees, he had cautioned they would soon wish they hadn’t.

“You’ll regret this, and you may regret this a lot sooner than you think,” McConnell wrote at the top of his commentary, quoting his own admonishment to Democrats as then-Majority Leader Harry Reid, a Democrat from Nevada, forced through that rules change.

Soon after, Republicans took control of the Senate and President Donald Trump won the White House. McConnell then made full use of the rules change he had decried to confirm scores of district and appeals court judges. He also employed the nuclear option again, this time to lower the filibuster threshold for Supreme Court nominees, allowing him to install Neil Gorsuch and Brett Kavanaugh to the high court, confirmations that would have been unlikely under the old rules.

Confirming so many judges has been a hallmark for Trump and McConnell, who both tout it as one of their most significant achievements as they each seek reelection.

“So, this is the legacy of the procedural avalanche Democrats set off,” wrote McConnell, predicting the “consequences of taking Sen. Reid’s advice will haunt liberals for decades.”

McConnell’s institutionalist message dropped unexpectedly in the middle of a long August recess. It came in the wake of multiple mass shootings including in El Paso, Texas, and Dayton, Ohio, that have rekindled a national debate over gun control. McConnell declined to call the Senate back into session to address the politically-divisive issue but said it would be discussed when senators return in September. McConnell has not endorsed any proposed changes to gun laws and right now it’s not clear anything can pass the Congress, especially after Trump waffled on what he might support after being lobbied by the National Rifle Association.

McConnell used his op-ed to blast liberal policies coming from the presidential campaign trail as reason to ensure 60 votes are needed to pass any major laws and said Republicans would take a long view, recognizing majority control in the chamber can go back and forth with each election.

“My Republican colleagues and I have not and will not vandalize this core tradition for short-term gain. We recognize what everyone should recognize — there are no permanent victories in politics. No Republican has any trouble imagining the laundry list of socialist policies that 51 Senate Democrats would happily inflict on Middle America in a filibuster-free Senate,” McConnell said.

Democratic presidential candidates such as Sen. Elizabeth Warren of Massachusetts and Sen. Kamala Harris of California have said they would back changing the filibuster for legislation, so that a filibuster could be broken by a simple majority vote and not the 60 votes currently required.

Senate Minority Leader Chuck Schumer, a Democrat from New York, has declined to say exactly what he would support until after the election, but he told reporters recently that “nothing is off the table.”

Reid defended his use of the nuclear option in his own New York Times op-ed earlier this month and embraced weakening the legislative filibuster because he said the Senate has become an “unworkable legislative graveyard.”

“If future Democrats shortsightedly decide to reduce the Senate to majority rule, we’ll have lost a key safeguard of American government,” McConnell at the end of his op-ed. “And — stop me if you’ve heard this one — they’d regret it a lot sooner than they think.”