One of Donald Trump’s Cabinet nominee has galvanized more opposition than any other: Betsy DeVos, the conservative billionaire philanthropist whom Trump has nominated to head the Department of Education.

She’s inspired hashtags, a “wear red day” revolt among teachers, and an aggressive critique from sitting Democrats. In recent days, her critics have reportedly overwhelmed phone lines urging senators to oppose her nomination when it comes up for a vote this week.

Take, for example, the nerve she’s struck among North Dakotans. Wall Street Journal reporter Reid Epstein reported Monday what he’d heard from Sen. Heidi Heitkamp:

Heitkamp a no on DeVos. Release notes: "95% of the almost 1,400 North Dakotans who contacted Heitkamp about DeVos opposed Devos nomination." — Reid J. Epstein (@reidepstein) January 30, 2017

Liberal opponents to the Trump administration’s policies have pushed critics to start calling Congress. At the Women’s March on Washington, filmmaker Michael Moore urged the half a million attendees and those watching on TV to call their representatives. Credo Action, a progressive activist group, has said its members alone made 18,000 calls to those on the Senate Health, Education, Labor, and Pensions Committee (which is responsible for DeVos’s confirmation hearings). As of Monday morning, a petition circulating on its website urging senators to “Block and resist Betsy DeVos’s confirmation as secretary of education” had received more than 1.4 million signatures.

Similarly, the office of Pennsylvania Democratic Sen. Bob Casey, in whose state Trump edged out a narrow victory, told Politico it received upward of 50,000 letters and emails opposing DeVos’s confirmation. Casey has said he will vote no on DeVos.

The flurry of opposition is tied to DeVos’s long history of activism for school choice, particularly voucher programs. Her inexperience with public education was evident in her confirmation hearing last week, where she blundered basic questions about education policy and stated that schools might need guns to “protect from potential grizzlies.” While many Democratic senators, like Bernie Sanders and Elizabeth Warren, have been vocal in their opposition to DeVos, Republican senators haven’t suggested they won’t back her.

Meanwhile, the frenzy of DeVos opposition also seems to have created cases where constituents could not reach their senators because of the volume of calls and messages from out of state. The office of Sen. Lisa Murkowski, a Republican from Alaska, has been inundated with out-of-state calls opposing DeVos.

“One of our state offices guessed they received over 150 calls in one day, and all but a couple were from out of state,” said Murkowski spokesperson Karina Petersen told ADN.com. A posting on Murkowski’s Facebook page directed constituents struggling to get through to her office to contact her via her website.

Historically, it’s rare for a Cabinet nominee to be outright rejected — the last time that happened was in 1989 with John Tower, George H.W. Bush’s nominee for secretary of defense. Sometimes, rather than allowing unpopular nominees to be rejected in the Senate, presidents ask them to withdraw themselves from consideration, as Presidents Obama and George W. Bush had to do.

Trump has given no indication that he would be willing to withdraw DeVos, however, and no Republican senators have spoken of plans to vote against her confirmation. Democratic Sen. Al Franken of Minnesota said in an interview with MSNBC’s Rachel Maddow last week that all Democratic senators would vote against DeVos — but they still need to convince at least three Republicans to oppose her nomination.