Dianne Feinstein. Justin Sullivan/Getty Images Senators are squabbling over the "blue slip process" that goes along with President Donald Trump's nomination of federal judges.

The process allows senators to essentially block a judicial nominee from their home state, giving Democrats one of their biggest pieces of leverage.

Republican leaders are mulling whether to alter the process as Democrats employ it more frequently.

Democrats are taking issue with Republicans' call for changes in the Senate Judiciary Committee's "blue slip" practice to both help clear the way for President Donald Trump to nominate more circuit court judges freely — and so his existing nominees can sail through confirmation.

The blue slip is a Senate tradition in which senators can give or withhold their blessing for a judicial nominee from their state. The process provides the party that does not control the White House with leverage over a good number of the president's nominations.

The process is intended to provide a more bipartisan consensus on judges who will serve in or represent a senator's home state when the president is of the opposition party, encouraging communication between the White House and home-state senators before a nomination. But the opposition party has sometimes used the blue slip process to stonewall nominations and prevent the president from naming judges in their states.

With Democrats now having the ability to — in many states — prevent Trump's judicial nominees from advancing, Senate Majority Leader Mitch McConnell told The New York Times recently that he thought the blue slip practice should be scrapped for circuit court nominations.

"My personal view is that the blue slip, with regard to circuit court appointments, ought to simply be a notification of how you're going to vote, not the opportunity to blackball," McConnell told the Times, adding that he still favored keeping the practice in place in its current form for district court judges.

Democrats called hypocrisy on McConnell's part. In 2009, right at the start of President Barack Obama's term, McConnell joined the entirety of the Republican conference in writing a letter to the president expressing their belief in the necessity of consultation with home-state senators for judicial nominations. The letter also stated that senators expected the blue slip process to be maintained "regardless of party affiliation."

"Republicans, Leader McConnell and [Senate Judiciary Committee] Chairman [Chuck] Grassley among them, have taken advantage of this tradition for decades," Democratic Sen. Sheldon Whitehouse, a Judiciary Committee member, told Business Insider in a statement. "People who claim to be Senate institutionalists should not engage in wholesale destruction of Senate traditions just for immediate partisan advantage."

Democratic Sen. Chris Coons of Delaware, another member of the Judiciary Committee, told Business Insider that the process has historically been "followed by members of both parties" and "ensures senators are consulted regarding nominees for seats from their home states."

"Judges are appointed with lifetime tenure, so it is critical that senators have the ability to secure judges for their home states that are qualified for their positions," Coons said.

"This isn't a partisan issue, either — this allows Republican senators to prevent Democratic presidents from confirming unqualified or inappropriate judges for their home states, and vice versa," he added.

Democratic Sen. Dianne Feinstein of California, the ranking member on the Judiciary Committee, issued multiple statements over the summer taking aim at those on the right who chastised the blue slip process.

"I want to set the record straight with respect to blue slips," she said in a July statement. "The blue slip has been used since 1917 and history is being misrepresented in a brazen attempt to destroy the Senate's prerogative to 'advise-and-consent' on judicial nominees. ... It was always honored during the Obama administration — even when Republicans did not return blue slips for up to two and a half years."

"The bottom line is that no circuit court nominee has been confirmed without two blue slips from home-state senators since at least 1981," she added. "As far as this senator is concerned, no senator should be chastised for thoroughly vetting nominees using a tool that's been around for 100 years."

But whether or not that tradition is followed is not up to McConnell. It comes down to whether Senate Judiciary Committee Chairman Chuck Grassley decides to stick with the process. Speaking to The Washington Times last week, Grassley said he hasn't made up his mind, telling the publication, "You need to ask me in a month."

For Trump, the judicial nominating process provides him with the opportunity to cement an early legacy, particularly as his legislative agenda has stalled in a Congress where both chambers are controlled by Republicans.

Trump has an unprecedented 140-plus vacancies to fill, some of which are the direct result of Republicans refusing to provide blue slips to Obama's nominees,. And 30 states have at least one senator who caucuses with Democrats. Though his nominees have received blue slips from Democratic senators in Colorado, Michigan, and Indiana, Trump has so far mostly avoided naming judicial nominees for district and circuit courts from states represented by at least one Democrat.

The blue slip issue turned hot recently after a trio of Democratic senators refused to provide blue slips for two of the president's judicial nominees.

The first such instance was when Democratic Sen. Al Franken of Minnesota refused to sign off on Trump's nomination of Minnesota Supreme Court Judge David Stras for a vacancy on the 8th US Circuit Court of Appeals earlier this month. Franken said he could not support Stras, nominated by Trump in March, after studying his record.

Franken was followed by Sens. Jeff Merkley and Ron Wyden of Oregon later in the same week. The Oregon Democrats announced they would block Ryan Bounds, an assistant US attorney in Oregon, from a seat on the 9th US Circuit Court of Appeals because he had not been approved by a bipartisan judicial selection committee in their state.

Republican Sen. Mike Lee of Utah, a member of the Judiciary Committee, told Business Insider in a statement that the blue slip process "should be used to prompt consultation between the Senate and the White House," but that it "isn't an invitation to thwart the president's power to nominate."

Several conservatives have taken issue with the blue slip process prior to McConnell making his remark last week. Some insisted that Democrats are using it just to stonewall Trump.

Carrie Severino, the chief counsel of the Judicial Crisis Network, a group that has gone to bat to defend Trump's nominees with large ad buys, told Business Insider in a recent interview that the practice "is not something" Democrats "can be allowed to abuse," adding that Democrats "are trying to create a filibuster of one."