Sen. Sherrod Brown (D-Ohio) on Friday said he will not sign off on two of President Trump's judicial picks, escalating a long-simmering fight over nominations in the Senate.

Brown said he will oppose the nominations of Chad Readler and Eric Murphy to serve on the 6th Circuit Court of Appeals.

"I cannot support nominees who have actively worked to strip Ohioans of their rights. Special interests already have armies of lobbyists and lawyers on their side, they don't need judges in their pockets," Brown said in a statement.

Because Brown is the home state senator for both Readler and Murphy he will receive "blue slips" allowing him to indicate whether he supports the nominations.

Jennifer Donohue, a spokeswoman for Brown, said that while the senator has not yet received the blue slips he does not plan to return them for either nominee.

That will force Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa) to decide if he will move forward with the nominations in the Judiciary Committee despite Brown's objections.

The "blue slip" rule - a precedent upheld by Senate tradition - has historically allowed a home-state senator to stop a lower-court nominee by refusing to return a sheet of paper, the "blue slip," to the Judiciary Committee.

But how strictly the precedent is followed is decided by the Judiciary Committee chairman - in this case, Grassley - and enforcement has varied over the years.

Donohue added that Brown "made very clear" to the White House that he couldn't support Readler or Murphy after meeting with them.

"Senator Brown actively tried to work with the White House and offered alternative choices - including respected conservative lawyers. He remains willing to work with the White House on alternative candidates that he could support," she said.

Two of Trump's circuit court nominees have previously been confirmed by the Senate despite one of their home-state senators not returning a blue slip.

Michael Brenna was confirmed to be a judge on the 7th Circuit Court of Appeals last month despite objections from Sen. Tammy Baldwin (D-Wis.), and David Stras was confirmed to serve on the U.S. Court of Appeals for the 8th Circuit in January.

Then-Sen. Al Franken (D-Minn.) refused to return his blue slip on Stras's nomination. Sen. Tina Smith (D-Minn.), Franken's successor, voted against Stras's nomination.

The Senate Judiciary Committee also advanced Ryan Bounds's nomination this week to serve on the U.S. Court of Appeals for the 9th Circuit, despite the opposition of both home-state Democratic Sens. Jeff Merkley (Ore.) and Ron Wyden (Ore.).

Republicans are confirming Trump's circuit court nominees at a record pace. They are poised to confirm more appeals court picks for Trump during his first two years than other recent presidents got in the same time period.

Grassley has defended his tactics, saying he will move forward with a circuit court pick when he feels like senators are trying to use the blue slip to obstruct Trump's nominees.

"First, it is completely false that I have 'done away' with the blue-slip courtesy. My blue-slip policy is the same as all but two of my 18 predecessors," Grassley said last month.