Senate Health, Education, Labor, and Pensions Committee member Al Franken seen January 31 during the committee's executive session on the nomination of Education Secretary-designate Betsy DeVos. AP Photo/Alex Brandon Lawmakers held the floor of the US Senate late Monday night in a final effort to tank the confirmation of President Donald Trump's nomination for education secretary, Betsy DeVos.

Democratic senators railed against DeVos on the Senate floor and on social media, calling her unfit to oversee the nation's education system. Sen. Al Franken of Minnesota called DeVos "fundamentally incompetent" on Monday.

"This is not a job for amateurs," Franken said. The senator challenged DeVos last month, when DeVos appeared to become confused during a line of questioning from Franken.

Kamala Harris, a freshman Democratic senator from California and former state attorney general, tweeted: "First and foremost, the country needs a Sec. of Education who has demonstrated basic competency when it comes to issues facing children."

Harris continued: "Half a million teachers would be put out of work under the Trump-DeVos plan. Devastating for our six million [California] students."

Protesters demonstrate against DeVos, President Donald Trump's nominee for secretary of education, on Monday in Washington, DC. Mario Tama/Getty Images

Senate Minority Leader Chuck Schumer of New York called DeVos "one of the worst nominees."

DeVos is a billionaire philanthropist and charter-schools advocate. Her nomination has been met with fierce opposition from lawmakers and from demonstrators who have been protesting her nomination in the streets of Washington.

Every Democrat in the Senate has vowed to oppose DeVos' confirmation, and two moderate Republicans said last week that they would not vote for her. Those moves set up a potential scenario in which Vice President Mike Pence may cast the deciding vote on Tuesday.