I think you can make a case that Pat Leahy did more damage to liberal interests than any individual Democratic senator of the Obama era, including the red state moderates:
The second reason for Trump’s outsized impact on the judiciary is that, when Democrats last controlled the Senate, one especially important Democrat — Judiciary Chair Patrick Leahy (VT) — took an unusually expansive view of the rights of the minority party.
An informal tradition known as the “blue slip” sometimes gives home-state senators an exaggerated influence over who gets confirmed to federal judgeships within their states (the tradition gets its name from blue pieces of paper that home-state senators use to indicate whether they approve of a particular nominee).
Traditionally, the Senate Judiciary Committee showed some level of deference to senators who disapprove of their home-state nominees, although the level of deference given to these senators varied wildly depending on who chaired the committee and whether that committee chair was politically aligned with the incumbent president.
Leahy, who chaired the Committee for most of the Obama presidency, gave home-state senators a simply extraordinary power to block judicial nominees. Under Leahy, a single senator of either party could veto any nominee to a federal judgeship in their state (although federal appeals courts typically oversee multiple states, each individual seat on these courts is traditionally assigned to a particular state).
Before Leahy, just one committee chair imposed such a rigid blue slip rule: Sen. James Eastland (D-MS), an arch-segregationist who took over the committee not long after the Supreme Court’s school integration decision in Brown v. Board of Education (1954). A strict blue slip rule allowed Southern senators to block judges who might try to desegregate public schools.
Leahy, to be clear, is not a segregationist. He’s a reliably liberal Democrat. But he nonetheless reinstated the Eastland Rule during his tenure as chair of the Judiciary Committee.
Leahy says that he did so to protect the “rights of the minority.” And protect Republicans he did. Red-state Republicans used the power Leahy gave them to hold many judicial seats open until Obama left office. Sen. Ron Johnson (R-WI) effectively held a seat on the United States Court of Appeals for the Seventh Circuit open for eight years until Trump could fill it.
It’s tough to estimate the full impact of Leahy’s adherence to the Eastland Rule. The rule often stopped the Obama White House from nominating anyone to a vacant judgeship. According to Daniel Goldberg of the liberal Alliance for Justice, Obama “did not even make a nomination” to two seats on the Fifth Circuit because the blue slip would have doomed anyone he named; those seats were eventually filled by Trump nominees.
In other cases, the blue slip allowed Republicans to drag out negotiations over a particular vacancy until McConnell took over the Senate in 2015 and imposed a blockade on nearly all of Obama’s appellate nominees.
The Eastland Rule also weakened Obama’s hand in negotiations with Senate Republicans, and sometimes forced him to name relatively conservative judges in order to placate senators who could veto judicial nominees. Sens. Saxby Chambliss (R-GA) and Johnny Isakson (R-GA), for example, effectively held one of Obama’s Eleventh Circuit nominees hostage until Obama agreed to also name Judge Julie Carnes — a George H.W. Bush district court appointee — to a second vacancy on that same court.
Republicans did not reciprocate when they came to power. Not long after Trump took office, then-Senate Judiciary Chair Chuck Grassley (R-IA) started confirming appellate court nominees over the objection of their home-state Democratic senators. (Republicans, for what it’s worth, have largely honored the blue slip tradition when a home-state senator objects to a district court nominee.)
What’s particularly amazing, as Millhiser says, is that Leahy wasn’t even upholding a Solemn Senate Tradition. The actual dominant norm before 2006 was that the failure to return a blue slip should be an important factor but not dispositive, with the only non-Eastland exception being a transparently cynical restoration of the rule by Orrin Hatch during the Clinton administration, which needless to say he did not restore when Republicans regained their Senate majority under Bush. The idea that Republican senators should be able to simply hold seats vacant for the next Republican administration was something Leahy really believed in on the merits, and he persisted in this belief no matter how transparently Republicans displayed their bad faith and no matter how obvious it was that they wouldn’t recicprocate. He didn’t merely uphold a Senate norms against the substantive interests of the party; he restored a long-abandoned one that had been used by segregationists to keep liberals and people of color off the courts just to justify his own piety about the World’s Greatest Deliberative Body (sic). It was just inexcusable behavior.