Dianne Feinstein, a Democrat, represents California in the U.S. Senate.

For 100 years the Senate has allowed home-state senators to play a central role in approving nominees for federal judgeships in their states.

For a judicial nomination to move forward, both senators from a nominee's state must return a "blue slip" that signals their agreement that that nominee should receive a hearing in the Judiciary Committee.

The blue-slip process was put in place to ensure judges nominated by the president are mainstream and well-suited to the state in which they would serve — not handpicked by special-interest groups based in Washington.

Republicans have long been on board with this tradition. In 2009, the entire Republican conference wrote to President Barack Obama, telling him they had to be consulted and would use the blue-slip process to block any nominees from their home states they didn't approve of.

Both parties have defended the blue slip to ensure senators play a role in selecting judicial nominees. Up until now.

Senate Republicans are threatening to eliminate the blue slip, the last remaining tool that ensures home-state senators of both parties play a role in the process of appointing judges.

Despite using the blue slip to block the nomination of Kentucky Supreme Court Justice Lisabeth Tabor Hughes to the U.S. Court of Appeals for the 6th Circuit, Senate Majority Leader Mitch McConnell (R-Ky.) is leading the charge.

He has now reversed the position he held during the Obama administration, arguing that the blue slip should be treated as a "notification" of how a senator intends to vote, even though Republicans used it to block nominees.

If successful, Republicans hope to stack the nation's courts with young, ideological judges who could radically affect civil rights, women's rights, workers' rights and the ability to check the ever-growing power of corporations over Americans.

Removing the only tool that prevents President Trump from choosing anyone he wants to sit on our federal courts could further weaken the judiciary's ability to serve as an independent check on the executive branch.

It's important to consider how we got here. Trump's ability to reshape our federal courts was made possible by unprecedented obstruction of Obama's judicial nominees, often through the use of the very blue-slip process that Republicans now want to dispense with.

Republicans allowed just 22 judicial confirmations in the final two years of the Obama administration, the fewest since President Harry S. Truman's administration.

By contrast, during the last two years of the George W. Bush administration, Senate Democrats confirmed 68 judicial nominees, including 10 judges on one day less than two months before the 2008 election.

As a result of this obstruction, Trump entered office with 88 district court vacancies and 17 circuit court vacancies.

While it's true that the nomination process has become more partisan, the blue slip maintains the integrity of the process. Now, fewer than 300 days into the Trump presidency, Republican senators may be willing to relinquish the Senate's responsibility to vet nominees, allowing ideological groups to supplant the input of home-state senators.

The Congressional Research Service found only three examples since 1979 of judicial nominees being confirmed without blue slips from both home-state senators. No circuit or district court nominee has been confirmed without blue slips from both home-state senators in nearly 30 years, regardless of which party controlled the Senate or White House.

During the Obama administration, Republican home-state senators weren't shy about using the blue slip to block judges — six circuit court nominees and 12 district court nominees never received hearings or votes because they didn't receive both blue slips. Nonetheless, Democrats never wavered from enforcing the policy, even though it meant Obama nominees were stymied.

Eliminating the blue slip now would prioritize short-term political gain while permanently diminishing the Senate as an institution and allowing all future presidents — Republican or Democratic — to disregard the input of senators on judges whose rulings would affect their constituents for decades.

The blue slip ensures that nominees are not only qualified but also chosen after consultation with senators. During the Obama administration, the White House often negotiated with Republican senators for months, if not years, to find mutually acceptable candidates. For example, a 10th Circuit nominee from Utah was recommended to the White House by Republican Sens. Orrin G. Hatch and Mike Lee.

The Trump White House thus far has shown little interest in adhering to norms around selecting candidates, instead choosing nominees for the 7th and 9th circuits without waiting for home-state senators' bipartisan selection committees to complete their work.

Just as Trump's judicial nominees will have an effect long after his presidency, the way the Senate vets judicial nominees and whether home-state senators continue to have a guaranteed seat at the table will also have a lasting legacy.

Republican senators should ask themselves if they're willing to permanently cede the Senate's "advise and consent" responsibility to the White House. When they're in the minority — and make no mistake, all of us eventually are — will it have been worth it?