Story highlights Multiple offices reported that a bulk of messages haves been related to Betsy DeVos

Not all calls are from senators' own constituents

Washington (CNN) An avalanche of phone calls is thundering across Capitol Hill as the Senate considers a slew of President Donald Trump's nominations, causing staffers to work continuously to field requests, complaints and other messages during an already busy time in the congressional calendar.

Matt House, a spokesman for Senate Minority Leader Chuck Schumer, said that as many as 1.5 million calls per day have been pouring into the Senate this week, according to data from Schumer's technical staff.

Multiple offices reported that a bulk of messages haves been related to Betsy DeVos, Trump's controversial pick for secretary of education. Her nomination moved ahead in the Senate on Friday, and she's expected to be narrowly confirmed Monday.

Teachers unions and liberal groups that are sharply opposed to her nomination have been urging members to vocalize their disapproval.

"DeVos has generated the most activity on our phones," said Josh Miller-Lewis, communications director for independent Sen. Bernie Sanders of Vermont. "We've had about 6,000 calls on DeVos and almost every single one has been urging a 'no' vote on her nomination."

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