Two of President Biden’s Cabinet nominees are slamming into confirmation hurdles on Capitol Hill, testing the White House’s ability to navigate a tenuous Senate majority amid deep partisan divisions in Washington.

Biden’s pick for the Office of Management and Budget (OMB), Neera Tanden, now appears unlikely to be confirmed after two Senate panels delayed business meetings to vote on her nomination Wednesday.

And Republicans are solidifying their opposition to Xavier Becerra, Biden’s pick to lead the Department of Health and Human Services.

Rep. Deb Haaland (D.N.M.), whose prospects were uncertain heading into Wednesday, received a significant boost later in the day when Sen. Joe Manchin (W.Va.), a key moderate Democrat, announced his support after previously declining to say whether he would vote for her.

The hurdles come despite a Democratic majority in the Senate following a pair of victories in Georgia’s runoff elections last month that created a 50-50 split, with Vice President Harris as the tie-breaking vote when needed.

Biden acknowledged disappointment with the pace of his confirmations in an exchange with reporters Wednesday, but he said the delayed transition slowed the process.

“I don’t so much blame it on the Senate, I blame it on the failure to have a transition that was rational,” Biden said. “We’re doing fine, I think we’re going to be in good shape.”

The confirmation challenges also underscore how fragile that Democratic majority can be, and how critical White House outreach to senators will be moving forward.