For years, senators have been able to effectively block judicial nominees from their home states through what’s known as the “blue slip” process.

But on Thursday -- amid Republican frustration over many of President Trump’s nominees being blocked -- Senate Republicans decided to override one such objection from a Democratic senator and confirm the nominee anyway.

Milwaukee attorney Michael Brennan was confirmed to fill an opening on the 7th U.S. Circuit Court of Appeals. Democratic Sen. Tammy Baldwin of Wisconsin had stalled Brennan’s nomination.

The seat has been open for more than eight years, the longest for the nation's appellate courts.

Until this year, it had been nearly three decades since the Senate confirmed a judge without two positive blue slips. Brennan's confirmation marked the second time it has happened this year.

STALLED JUDICIAL NOMINEES WILL BE CONFIRMED 'NO MATTER WHAT TACTICS' EMPLOYED, MCCONNELL SAYS

The maneuver comes as Senate Republicans are racing to confirm as many federal judges as they can before November's midterm elections when control of the Senate could flip to Democrats.

The Senate gives lawmakers a chance to weigh in on a judicial nominee from their home state by submitting a blue-colored form called the "blue slip." A positive blue slip signals the Senate to move forward with the nomination process. A negative blue slip, or withholding it altogether, signals a senator's objection and almost always stalls the nomination.

The move to go ahead with a hearing for Brennan and a vote on the floor had Democrats complaining that Republicans were eroding one of the few remaining customs in the Senate that forced consultation on judicial nominations. They also noted that Republicans used the blue slip to block one of President Barack Obama's nominees for the very same judgeship.

"I'd admonish my friends on the other side of the aisle, this is a very dangerous road you're treading," said Senate Minority Leader Chuck Schumer, D-N.Y. "As everyone knows, the winds of political change blow swiftly in America. The minority one day is the majority the next."

But Sen. Chuck Grassley of Iowa, the Republican chairman of the Senate Judiciary Committee, said Democrats' complaints were based on an incorrect understanding of the blue slip's history.

"The blue slip courtesy is just that -- a courtesy," Grassley said.

He said past chairmen of the committee had rarely used negative or unreturned blue slips as unilateral vetoes. The most recent exception was Democratic Sen. Patrick Leahy of Vermont, who was chairman during the first six years of Obama's presidency.

"That was his prerogative," Grassley said.

Still, the blue slip has been in use for more than a century and only a handful of judges have won confirmation during that time without two blue slips.

Grassley said that under his tenure, the blue slip will be used to ensure the president consults with home-state senators, but not as a veto for appellate court nominees. He said he was satisfied in Brennan's case that the White House consulted with both of Wisconsin's senators before the president nominated him.

Republicans have made it a priority to confirm the president's nominees, particularly those who will serve on federal appeals courts. It's a top issue with social conservatives leading into this year's midterm elections. With Democrats slow-walking many of Trump's nominees, McConnell said last October that the blue slip process should not be used to "blackball" nominees.

"We're going to confirm these judges. I don't care what tactics they employ," McConnell recently told Fox News's Martha MacCallum.

Fox News’ Doug McKelway and The Associated Press contributed to this report.