Sen. Mitch McConnell announced this week he is stepping down as Senate majority leader. In liberal circles, McConnell is often portrayed as a cynical Machiavellian schemer, with some justice. But in the history books—if there are any such things in a future United States of Trump—McConnell will be remembered as the man who wrecked the functionality and power of the Senate more than any other senator in American history.

First, McConnell was the driving force behind turning the Senate filibuster from an occasional mechanism mainly used to bottle up civil rights legislation into a requirement for almost every bill passed through regular order, which only dates back to about 2007. This means not only that senators representing as little as about 11 percent of the population can block ordinary bills, but it also has greatly damaged the basic process of legislation. Because nothing can be passed normally, a whole year or two’s worth of vital priorities tend to get jammed into 3,000-page super-bills negotiated and passed at the last second. It’s an absurd way to legislate, and it has all but ended the traditional Senate career. Being a senator today largely consists of automatically voting the party line on these bills and on nominees to various agencies.

Second, McConnell’s most passionate priority of his career has been "enclosure of our public life by money," as Alex Pareene writes. For decades, he has worked diligently to roll back and eventually destroy as many restrictions on the use of private money in politics as possible. This enabled his own fundraising, but it also meant power flowed from the Senate to the billionaire class, many of whom are Newsmax-addled cranks who prop up nutty GOP Senate candidates that lose winnable elections. Meanwhile, the fact that political parties are still relatively restrained in their fundraising means leaders like McConnell have few ways to discipline their lunatic fringe.

Third, McConnell’s second-most passionate priority has been stuffing the judiciary full of Federalist Society goons whose legal views begin and end with "laws passed by Democrats are unconstitutional." Most notably, he broke all precedent and violated the Constitution by refusing to hold so much as a hearing for President Obama’s nominee to replace Justice Antonin Scalia. McConnell was rewarded by Trump rubber-stamping hundreds of exactly the kind of nominee McConnell loves, including three Supreme Court justices.

But the effect of this has been an imperialist judiciary steadily arrogating the powers of Congress to itself. Right now, there is a case that would overturn the Chevron doctrine, which holds that judges should defer to agencies in cases where statutory language is unclear. If the Supreme Court rules as expected, this will destroy the administrative state as we’ve known it for a century, and eviscerate the power of Congress in the process.

Instead of representatives and senators writing laws that instruct the executive branch about how and what kind of things to regulate (food, water, pollution, air travel, and so on) random judges will do it in concert with their oligarch pals. Right-wing billionaires will fund thousands of lawsuits against whatever regulations they don’t like, and—in between the same billionaires and members of the judiciary enjoying some ultra-luxurious vacations together—right-wing judges will rule in their favor. And thanks in part to how McConnell has gummed up the gears of Congress, it is all but helpless to respond to this assault on democracy.

The Constitution is supposed to create a separation of powers because, the framers assumed, any member of an institution would surely seek to protect and expand the powers of that institution. "Ambition must be made to counteract ambition," says Federalist No. 51. But they didn’t anticipate Mitch McConnell, a man willing to get elected to the Senate to destroy it and set up judicial tyranny ten times worse than that of King George III.