The Senate Democrats’ move last year to eliminate filibusters on most nominations — it now takes only a simple majority to confirm — has helped President Obama dramatically increase his impact on the federal judiciary for years to come.

Obama, approaching the end of his sixth year in office, is on track to put 305 judges on the federal bench — 252 on district (trial) courts and 53 on appeals courts. At this point, he’s well ahead of George W. Bush’s 256 total appointments at the six-year mark and close to Bush’s final total of 324 appointees. He’s just six behind Bill Clinton’s six-year total.

But in January, Obama will, for the first time in his presidency, face a Republican-controlled Senate. And the GOP rancor sparked by the Democrats’ November 2013 rule change — known as the “nuclear option” — could well limit future confirmations. In addition, a bipartisan deal struck in 2013 that greatly shortened the amount of debate required for judicial nominees is set to expire next year.

Even so, Obama’s impact on the courts has been dramatic. As we wrote in May, when Obama took office in 2009, 10 of the 13 U.S. courts of appeal had Republican majorities. Now, nine of them have Democratic majorities.

With the last dozen pending judicial nominees confirmed Tuesday night, the filibuster change has boosted Obama’s total judicial confirmations this year to 89, by far his highest yearly total and the second-highest among the last three presidents. (Clinton had 99 confirmed in 1994, and Bush’s high was 72 in 2002.)

What’s more, the nation’s courts are approaching what might be called “full employment” status. Only seven of the judiciary’s 179 appeals court seats are vacant, according to the Administrative Office of the U.S. Courts. And only 31 of the country’s 677 district court seats were unfilled when the Senate adjourned Wednesday.

“There’s no doubt it had an impact,” said the Brookings Institution’s Russell Wheeler, an expert on the federal judiciary, especially on the appeals courts, though it’s unclear whether the effect is “limited or massive.” There are multiple variables in play.

For example, 15 judges have been confirmed with fewer than the 60 votes that had previously been required to overcome a filibuster, according to statistics compiled by the Alliance for Justice.

But it’s not clear whether some of those voting “nay” were voting against the nominee or in protest of the rule change.

On the other hand, Wheeler said, it’s clear that, before the rule change, the Senate was confirming only 71 percent of Obama’s appeals court nominees and 77 percent of his district court nominees. The rule change allowed Obama to boost the overall confirmation rate for his presidency to more than 90 percent — slightly higher than Clinton’s or Bush’s.

That success has come at a cost. Republicans, enraged by Senate Majority Leader ­Harry Reid’s action, retaliated by slowing the confirmation process, forcing recorded votes to end debate on virtually all judicial and executive branch nominees — many of whom were eventually unanimously, or nearly unanimously, confirmed.

As a result, lifetime-appointee judges on the bench and hundreds of ambassadorial and other executive branch nominees were forced to wait many months in limbo.

Historically, most judicial nominees, especially those for district court seats, got confirmed “pretty easily,” said Doug Kendall, president of the Constitutional Accountability Center. Democrats are, of course, hardly blame-free when it comes to blocking Republican judicial nominees. But this time, Kendall noted, “it took the nuclear option” to break through the solid GOP opposition to Obama’s picks.

The difference is especially pronounced on some appeals courts — especially the District of Columbia Circuit, where federal legislation and regulations are often reviewed. (It was the heated dispute over Obama’s nominees to that court that helped trigger the nuclear option.)

The question for court watchers these days is, now that the Republicans have retaken the Senate with a 54-to-46 majority, has Obama seen his last judicial nominees confirmed?

“No one knows where the rank-and-file are on this question,” Kendall said.

Some observers have predicted that Republicans would also be certain to block Obama’s nominees. But other observers, on both sides, believe otherwise.

For one thing, both Clinton and George W. Bush got more than 60 judges confirmed in their last two years in office, though the opposing party controlled the Senate, according to Kyle Barry of the liberal Alliance for Justice.

“It would be myopic,” he wrote recently, to look at the GOP anger over the filibuster rule change and “conclude that, with a Republican majority, the confirmation process will grind to a halt.”

The filibuster change “meant that Republicans knew that, no matter how strong a case they had against a nominee, the nominee would likely be confirmed,” said Ed Whelan, who heads the conservative Ethics and Public Policy Center.

But it is “an unrealistic expectation that there will be zero judges confirmed over the next two years,” Whelan said.

“Republican senators will have lots of leverage over nominations,” he said, “but if the White House makes reasonable efforts to accommodate them, there’s plenty of room for deals.”

Senate Democrats and Republicans have continued their heated debate over the effect of the rule change.

Democrats have reveled over the past week over Obama’s judicial confirmation rates and the huge increase in his appointees on the courts.

“There’s clearly a number of nominees that wouldn’t have gotten through without the change in rules,” Sen. Chris Murphy (D-Conn.), a freshman who is part of the large contingent of relatively new Democrats who pushed Reid to make the move, told our colleague Paul Kane. “I think it was a common-sense rules change, and I think this last week has borne out the importance of getting it done.”

Veteran Republicans counter that the overwhelming majority of the nominees would have won confirmation under the old rules as well, and that the only big change was the ability to stack the D.C. Circuit — the second most important federal bench.

“They took the most damaging step to the ability of the Senate to be a consensus-building institution, in the Senate’s history, and they got nothing out of it except three circuit judges, and they made it harder for them to confirm everybody else,” Sen. Lamar Alexander (R-Tenn.), said Tuesday. Alexander negotiated previous efforts to avert the unilateral rule change.

Alexander pointed out that Clinton dealt with a GOP majority in the Senate in his sixth year — during which, according to the Alliance for Justice data, he was able to get 65 judges confirmed. The Republican retaliation has been to force Reid to jump through every procedural hurdle for almost every nominee coming down the pike, meaning that traditions such as approving many lower court nominees by a unanimous voice vote has almost disappeared.

Reid “dug a big hole, not just for himself but for the Senate and the president,” Alexander said.

— With Colby Itkowitz

Twitter: @KamenInTheLoop, @ColbyItkowitz