WASHINGTON - Democrats announced plans Monday to hold the Senate floor around the clock to protest Republicans' push to confirm President Donald Trump's Cabinet picks.

Democrats' effort got under way as the Senate headed toward a showdown vote Tuesday on Education Secretary nominee Betsy DeVos, a wealthy GOP donor who has advocated for alternatives to public education. DeVos' nomination has drawn particularly fierce opposition from teachers' unions and others. Two GOP senators have announced plans to oppose her, which could result in a 50-50 Senate vote Tuesday. That would leave Vice President Mike Pence in the role of tie-breaker, something that has never happened with a Cabinet nominee in the Senate's history, according to the Senate historian.

"Democrats will hold the floor for the next 24 hours until the final vote to do everything we can to persuade just one more Republican to join us," Sen. Patty Murray, D-Wash., said on the floor around mid-day Monday. "And I strongly encourage people across the country to join us — to double down on your advocacy — and to keep making your voices heard for these last 24 hours."Republicans accused Democrats of slow-walking 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 secretary of Health and Human Services, 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 series of 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 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. Republicans control the Senate with a narrow 52-48 margin, yet there is very little suspense about the final outcome on any of the nominees. That's 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 in the 100-seat Senate, not the 60 votes previously required.