The U.S. Senate could vote this week to fill a longstanding federal court vacancy for Wisconsin over the objection of Democratic U.S. Sen. Tammy Baldwin.

The vote by GOP senators would clear the way for Milwaukee attorney Michael Brennan to fill a seat on the 7th Circuit Court of Appeals in Chicago that has been open since 2009, making it the longest such vacancy in the country.

President Donald Trump nominated Brennan in 2017 after two previous nominees by former President Barack Obama never received votes in the Senate.

"It sends the message that obstruction pays," said University of Richmond School of Law professor Carl Tobias. "That's a seat that by all rights should have been filled during the Obama administration."

Most recently, Republican senators decided not to vote on Obama nominee Donald K. Schott despite Schott's support from a bipartisan judicial nominating panel and endorsements from both Baldwin and her Republican colleague, Wisconsin U.S. Sen. Ron Johnson.

Republicans currently hold a 51-49 majority in the Senate. Republican U.S. Senate Majority Leader Mitch McConnell has scheduled what's referred to as a cloture vote for Brennan and five other Trump appeals court nominees this week, which would cut off debate on their nominations.

Several liberal groups held a media conference call Monday to urge Republicans to hold off, saying both the nominating process and Brennan's own record were disqualifying.

One Wisconsin Now program director Analiese Eicher criticized Brennan's work chairing Gov. Scott Walker's Judicial Selection Advisory Committee, where he supported Walker's appointment of state Supreme Court Justices Rebecca Bradley and Daniel Kelly.

"Anyone who thinks that individuals with views like Bradley and Kelly are state Supreme Court justice material really has no business being considered for a lifetime appointment to the federal bench," Eicher said.

In addition to his work as a private attorney, Brennan was a Milwaukee County Circuit Court judge from 2000 until 2008. He was also once a law clerk for the 7th Circuit Court of Appeals.

When Trump nominated Brennan last year, Johnson immediately praised the move.

"The White House made a great decision in nominating Mike Brennan," Johnson said in an August 2017 statement. "Wisconsin, the 7th Circuit, and our nation's judicial system will be well served once he is confirmed by the Senate."

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But the Brennan nomination is bypassing a Senate tradition that several Republicans — and even Brennan himself — defended during the Obama presidency.

The Senate had previously operated under a process that let senators support nominees from their home states by turning in what are known as "blue slips." Conversely, a single senator could block a nominee by withholding their blue slip.

For example, Johnson withheld his blue slip in 2011 after Obama nominated Victoria Nourse to the 7th Circuit. Brennan wrote in an op-ed at the time Johnson should have his say.

"There are now two senators from Wisconsin from different political parties, so to exclude Johnson and those citizens who voted for him would be a purely partisan move," Brennan wrote at the time. "Johnson represents millions of Wisconsin citizens."

The U.S. Senate, which was under Democratic control at the time, honored Johnson's objection, and the Nourse nomination did not move forward.

Baldwin referenced Brennan's op-ed in a letter she wrote to U.S. Sen. Charles Grassley, the chairman of the Senate Judiciary Committee, the first stop for judicial nominations.

"I am troubled that I am not being afforded the same consideration that had previously been provided to our Republican colleagues, including Senator Johnson" Baldwin wrote in January.

Baldwin also said Brennan failed to garner a supermajority from the bipartisan commission set up by Baldwin and Johnson to recommend judicial nominees. Brennan received four votes from the six-member panel.

Schott, the Obama nominee from 2016, failed, received five votes from the commission in addition to support from Baldwin and Johnson.

The 7th Circuit Court of Appeals covers Wisconsin, Illinois and Indiana. It has heard several high-profile cases in recent years, including challenges to Wisconsin’s voter ID and right-to-work laws.

Baldwin has also opposed Gordon Giampietro, whom Trump nominated to be a federal district court judge in Milwaukee.

Americans for Prosperity, a conservative group funded by wealthy political activist brothers Charles and David Koch, has prioritized supporting Brennan and other nominees to the federal judiciary. If confirmed, federal judges can remain on the bench for life.