For the first time in more than three decades, Republican-appointed judges will soon occupy nearly half the seats on the left-leaning 9th Circuit Court of Appeals -- dealing a setback to progressive legal advocates who have long seen the court as a safe bet for favorable rulings.

The radical transformation of the San Francisco-based court is largely the result of President Trump's aggressive push to nominate conservative judges and bypass traditional consultations with Senate Democrats -- a practice that has led to repeated howls of protest from California's two Democratic senators, Kamala Harris and Judiciary Committee ranking member Dianne Feinstein. The 9th Circuit has a sprawling purview over cases arising in nine western states, including California, Hawaii, and Oregon.

Once Trump's latest picks to the 9th Circuit, including Ken Lee and Dan Collins, are confirmed as expected and remaining vacancies are filled, 13 of the 29 active seats on the key appellate court will be filled with judges picked by Republican presidents. At this time last year, 16 judges on the 9th Circuit were appointed by Democrats, with only six chosen by Republicans.

"As the 9th Circuit shifts to become more conservative and better parallels the Supreme Court's ideological baseline, I could only imagine fewer liberal 9th Circuit decisions and fewer overturned 9th Circuit decisions generally," legal scholar and judicial data guru Adam Feldman, who blogs at Empirical SCOTUS, told Fox News.

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"As a general statement, with the death of [9th Circuit Judge Stephen] Reinhardt and Trump's push for conservative judges to fill the circuit, I suspect that there will be a noticeable shift in a portion of ideological case outcomes," Feldman added.

The circuit has had a reputation for seeing its decisions reversed by the Supreme Court. But citing data from the Supreme Court Database, which is widely used by scholars, Feldman noted that the number of liberal decisions from the 9th Circuit that the Supreme Court has chosen to review has diminished since the beginning days of the Roberts Court in 2006.

"The general notion that the Supreme Court may not be looking to overturn liberal 9th Circuit decisions to the same extent as it has in the past is clear," Feldman said.

Cases before the 9th Circuit are typically heard by randomly selected three-judge panels, out of a pool that includes the 29 active judges and a group of several senior status judges, which is currently evenly divided among conservative and liberal jurists. In certain cases, the entire 9th Circuit can choose to hear a case en banc, which would result in a randomly chosen 11-member panel reviewing the three-judge panel's decision.

In both scenarios, conservative judges will soon have a historically high chance to occupy the majority on the panels. That's good news for Republicans, who have complained that the 9th Circuit has repeatedly stood in the way of the Trump administration with a slew of injunctions on matters like asylum law and the travel ban, only to later be overturned by the Supreme Court.

“We’re very happy to have these extraordinary nominees,” Carrie Severino, chief counsel for the Judicial Crisis Network, told The Daily Signal in February. “It doesn’t change the [9th Circuit] majority to Republican nominees. But when we are talking about future three-judge panels, the odds are a lot better.”

Feldman has found that, while the 9th Circuit's decisions are more often reviewed by the Supreme Court, that owes to its large caseload and sweeping purview over several Western states. The 9th Circuit is overturned in 79 percent of the cases taken by the Supreme Court, Feldman found -- more than any other appellate court except the Sixth Circuit, although three other courts have an overturn rate above 70 percent.

Many of the 9th Circuit's cases, however, have been high-profile, with sweeping implications for executive power and the Trump administration's agenda. Just weeks ago, the 9th Circuit broke ranks with another federal appellate court and ruled that a Sri Lankan man who failed his initial asylum screening had the constitutional right to go before a judge -- threatening to clog the immigration court system further with tens of thousands of similar claims per year and setting up a likely Supreme Court showdown.

Meanwhile, left-leaning legal groups repeatedly have brought big cases directly to the 9th Circuit during the Trump administration. Ben Feuer, one of the top appellate litigators in California and chairman of the California Appellate Law Group, told Fox News that progressives are unlikely to look to other circuits now that the 9th Circuit is turning more conservative.

"Aside from the 9th Circuit, only the Second and Eleventh Circuits currently have a majority of Democratic appointees (the Tenth is tied)," Feuer said. "The Second Circuit is +5 Democratic by my count and the Eleventh is +2 Democratic. Those aren't very significant differentials -- certainly not on par with the Ninth Circuit of yore."

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Feuer added: "Now, if the trend continues, that could certainly change, but I don't know that filing suit with left-leaning outcome goals in New York or Miami is very likely to get a much different result than in San Francisco, Los Angeles, or Seattle. Also, many of the more progressive state statutes being enacted are coming from the experimental West Coast cities and states, so those have to be litigated in the Ninth Circuit anyway."

In televised remarks last Thursday, Feinstein warned that a future Democratic administration would immediately move to load the 9th Circuit with more liberal justices, given the Trump administration's no-compromise approach. But, Feuer said, that may not be entirely within Democrats' control.

"We're only recently into the filibuster-free 'post-nuclear' era in judicial appointments, in which simple majorities in the Senate can confirm nominations," Feuer said. "That means that if a party controls both the presidency and the Senate, they'll get in pretty much whoever they want -- so if the Democrats get both, there will surely be some vacancies and the balance may well shift back ... But we don't really know what it means when the presidency and the Senate are split."

He noted that in such scenarios in the past, the president would tend to compromise with more center-leaning nominees but questioned whether that would be the case going forward.

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"Perhaps a split between the presidency and the Senate would mean no new appointments of any kind," Feuer speculated.

The 9th Circuit, meanwhile, could still grow. The Judicial Conference of the United States, which was created by Congress to advise on federal court matters, has recommended creating five new appellate judge positions and 17 new trial judge positions for the 9th Circuit, given its growing caseload.

Should Congress opt to create those five slots -- in the same way the post-Watergate Democrat-controlled Congress added 10 judges to the 9th circuit in the late 1970s -- GOP appointees could surge to an unprecedented 18-16 majority on the 9th Circuit.

Such a move, however, would require the consent of the House, which is currently under Democratic control.