The vote planned around 12 noon EST Tuesday will come after Democrats undertook a marathon speaking session deep into the night in a show of opposition to the nominee, Betsy DeVos. She is a wealthy GOP donor who has devoted herself to boosting alternatives to public education, sparking concerns among educators that she won’t be a strong champion for the nation’s public school systems.

Two GOP senators, Susan Collins of Maine and Lisa Murkowski of Alaska, have announced plans to oppose DeVos in a Senate split 52-48 between Republicans and Democrats. That will leave her with a tie vote if all other Republicans support her and all Democrats oppose her as expected, and will require Pence to put her over the top. A vice president breaking a tie on a Cabinet nomination would be a first in the history of the Senate, according to the Senate historian’s office. And a Republican senator, South Carolina’s Time Scott, went to the floor to speak, saying the focus should be on improving public education and not on DeVos.

Emotions ran high ahead of the vote as constituents jammed senators’ phone lines with calls and protesters gathered outside the Capitol, including one person in a grizzly bear costume to ridicule DeVos’ comment during her confirmation hearing that some schools might want guns to protect against grizzlies.

“Mrs. DeVos demonstrated a complete lack of experience in, knowledge of and support for public education. She was unable to address basic issues that any New Hampshire school board member could discuss fluently,” said Sen. Maggie Hassan, D-N.H., whose son has cerebral palsy but studied in public schools under a federal law that guarantees access for disabled students. Several Democrats questioned DeVos’ commitment to and understanding of that law.

But Republicans accused Democrats of slow-walking DeVos and other qualified nominees to placate liberal base voters who still haven’t come to terms with Trump’s election.

“It seems this gridlock and opposition has far less to do with the nominees actually before us than the man who nominated them,” said Senate Majority Leader Mitch McConnell, R-Ky. “Enough is enough.”

In addition to DeVos, Republicans hope to confirm a series of other divisive nominees this week: Alabama Republican Sen. Jeff Sessions as attorney general, GOP Rep. Tom Price of Georgia as health secretary and financier Steven Mnuchin as treasury secretary.

In each case Democrats intend to use the maximum time allowed under the Senate’s arcane rules to debate the nominations, which may result in a late-night votes this week and delay Mnuchin’s approval until Saturday.

Republicans complain that previous presidents have been able to put their Cabinets in place more quickly. Democrats say it’s Trump’s fault because many of his nominees have complicated financial arrangements and ethical entanglements they claim they have not had enough time to dissect. Thus far, six Cabinet and high-level officials have been confirmed, including the secretaries of state, defense, homeland security and transportation.

The clash over nominees has created a toxic atmosphere in the Senate that mirrors the tense national mood since Trump’s election, with Democrats boycotting committee votes and Republicans unilaterally jamming nominees through committee without Democrats present. Yet there is little suspense about the final outcome on any of the nominees because Democrats themselves changed Senate rules when they were in the majority several years ago so that Cabinet nominees can now be approved with a simple majority, not the 60 votes previously required.