“Power tends to corrupt,” Lord Acton wrote to Bishop Mandell Creighton in 1887, “and absolute power corrupts absolutely.” One form of that corruption is partisan hypocrisy, doing an about-face on a significant issue for no reason other than enhancing your own political party’s power. That is playing out before our eyes as Senate Democrats who once defended that institution now appear poised to damage it forever.

A century before Acton’s famous words, America’s Founders designed our system of government to keep too much power from ending up in too few hands. Their design is captured by the phrase “checks and balances.” The accumulation of all powers in the same hands, wrote James Madison, “may justly be pronounced the very definition of tyranny.”

Checks and balances operate within, as well as between, the three branches of government. The Senate and House, for example, participate in the legislative process in different ways. Senate rules require a supermajority to end debate before a simple majority can pass a bill. That gives the minority more influence and encourages deliberation and consensus. This opportunity for extended debate has been the single most defining feature of the Senate as a legislative body for more than 200 years.

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The 60-vote threshold required since 1975 is the lowest since the turn of the 19th century. For more than a century, ending debate required 100 percent agreement, dropping to two-thirds from 1917 to 1975. It is still high enough so that moving legislation forward requires at least minimal bipartisan effort. A filibuster occurs when the tally falls short of that 60-vote target. Extended debate obviously empowers the minority and frustrates the majority, but both parties have used it to their advantage across a wide range of legislative issues.

It’s easy for senators to defend extended debate when their party is in the minority. The real test comes when Senate control changes and those senators must apply their earlier arguments to themselves. In April 2005, for example, when Democrats were in the minority, Senator Charles Schumer (D., N.Y.) said, “When the Senate does slow things down, when the Senate does invoke checks and balances, the Republic is better off.”

A month later, with Republicans holding a 55–45 majority, Schumer again addressed extended debate. He explained that the Senate “is not like the House of Representatives. . . . The reason we don’t always work by majority rule is very simple. On important issues, the Founding Fathers wanted – and they were correct in my judgment – that the slimmest majority should not always govern.”

Sen. Patrick Leahy (D., Vt.) shared Schumer’s position, addressing rumors that Republicans were considering a strategy to abolish nomination filibusters. “When you have a slim majority,” Leahy said, “and are willing to use parliamentary brute force . . . you can. It does not make it right. It makes it wrong.” He said using a parliamentary gimmick to eliminate the filibuster would be “an abuse of power to advance a power grab” and to “undercut the checks and balances of the Senate.”

They say be careful what you wish for, because you might just get it. The 2006 election handed Democrats an even narrower 53–47 Senate majority and, with it, the chance to put their actions where their words once were. In 2013, however, Schumer, Leahy, and their fellow Democrats used the very “parliamentary brute force” Leahy once condemned to pull off the “abuse of power to advance a power grab” that he had opposed to abolish filibusters of nearly all nominations.

We now face a similar, but more significant, challenge. Extended debate had not been part of the confirmation process until Democrats used it to defeat nominations less than 20 years ago. It has, however, been an integral part of the legislative process since the turn of the 19th century. Today, Democrats have the slimmest majority possible in a 100-member body, and yet are threatening to abolish the legislative filibuster so they can pass whatever legislation they want and ignore the minority altogether.

Four years ago, 61 senators signed a letter saying that they would oppose “any effort to curtail the existing rights and prerogatives of Senators to engage in full, robust, and extended debate as we consider legislation before this body in the future.” Twenty-seven Democrats who signed that letter serve in the Senate today and another, Vice President Kamala Harris, is president of the Senate. “We are united,” they wrote, “in our determination to preserve the ability of Members to engage in extended debate when bills are on the Senate floor.”

The 27 current Senate Democrats who signed that letter have all been big fans of the legislative filibuster, together voting to block legislation more than 2,800 times. Add in the rest, and the senators in today’s “majority” have voted to filibuster legislation 4,529 times. And President Joe Biden,  when he was a senator, voted to filibuster legislation nearly 140 times himself.

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Senator Dianne Feinstein (D., Calif.) pledged to oppose “any effort to curtail” the legislative filibuster that she has voted for 205 times. So did Leahy, who has voted to do so 228 times, and Senator Jack Reed (D., R.I.), who has 198 filibuster votes to his credit. Are they just as “united” in their “determination” to oppose any changes to extended debate now that they have the majority?

Is parliamentary brute force, especially with now the slimmest possible majority, still an abuse of power to advance a power grab? Is the Republic still better off when the Senate maintains its checks and balances? Or has power so corrupted Senate Democrats that they will simply abandon all of what they claimed the Founders had in mind and what they themselves proclaimed only a few years ago? Actions certainly do speak louder than words.