FILE - Sen. Joe Manchin, D-W.Va., left, walks with Sen. Kyrsten Sinema, D-Ariz., with Sen. Patty Murray, D-Wash., behind them at center, after attending a Democratic policy luncheon, on Nov. 16, 2021, on Capitol Hill in Washington. While Manchin and Sinema’s opposition to changing Senate rules stalled the party's signature voting legislation this month, they have been reliable votes on President Joe Biden's nominees to the courts. The two Democratic senators will be the center of attention as Biden moves forward with a pick to replace the retiring Justice Stephen Breyer. (AP Photo/Jacquelyn Martin, File)

Democrats in Congress have fractured repeatedly over President Joe Biden’s agenda, stalling legislation and creating an atmosphere of mistrust that has made it increasingly difficult for progressives and centrists to work together.

But one area where the party has not cracked, not even an inch, is on Biden’s nominations to the courts.

That ironclad unity has helped Biden appoint the most judges during the first year of a presidency since John F. Kennedy. The achievement is giving Democrats hope that the coming fight over the Supreme Court seat will allow them to go on the political offensive and move past an ugly stretch of legislating that depressed their base.

But unity is far from assured as Republicans prepare to oppose what they predict will be a “radical” Biden pick to replace the retiring Justice Stephen Breyer.

As always, two Democratic senators will be the center of attention: Joe Manchin of West Virginia and Kyrsten Sinema of Arizona.

While their opposition to changing Senate rules stalled the party’s signature voting legislation this month, they have been reliable votes on Biden’s nominees to the courts. Indeed, in the 44 roll call votes held so far on Biden’s judicial picks, there has yet to be a single Democratic defection.

That streak bodes well for the future nominee in the 50-50 Senate, where Vice President Kamala Harris would break any ties. If Democrats are able to stay together, Republicans would lack the power to stop Biden’s pick from being confirmed. Supreme Court nominees can no longer filibustered, thanks to a rules change put in place by GOP leader Mitch McConnell of Kentucky, making party unity the path to certain victory.

On this particular vote, analysts suspect that Democrats will have a better chance of staying united than Republicans.

“I’d say the progressive wing probably has less to worry about than McConnell & Company,” said Russell Wheeler, a visiting fellow at the Brookings Institution who closely tracks the judicial nomination process. “But you just never know.”

Yet the news of Breyer’s pending retirement — he plans to leave at the end of the court’s term — drew cautious, noncommittal responses from both Sinema and Manchin.

Sinema tweeted that she would examine Biden’s pick on three criteria: “whether the nominee is professionally qualified, believes in the role of an independent judiciary, and can be trusted to faithfully interpret and uphold the rule of law.”