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."
Democratic Sen. Dianne Feinstein, who hails from the much larger state of California, has been inundated with messages. Her spokesman, Tom Mentzer, said their office has received 80,000 calls in opposition to DeVos, 40,000 against Trump's pick of Sen. Jeff Sessions for attorney general and 25,000 on newly sworn-in Secretary of State Rex Tillerson.
Those are just three of the close to two-dozen cabinet level positions needing confirmation by the Senate at the start of a new presidency. On top of that, Trump recently picked his first Supreme Court nominee, a post that traditionally generates a swarm of attention.
Congress is also at the beginning of high-profile legislative debates that will affect millions of people, like the fight over Obamacare and immigration -- two issues that see heavy involvement from large activist organizations.
Plus, Trump has issued almost as many executive orders as the number of days he's been president, some of which, like the executive action on immigration, drew a widespread emotional reaction from voters.
A spokesman for Republican Sen. James Lankford of Oklahoma said their office normally gets 150-200 calls per week but has taken 4,600 calls in the past two weeks, with the primary topics including the temporary travel ban, cabinet nominees, Trump's chief strategist Steve Bannon, Obamacare, and the US-Mexico border wall proposal.
While a new Congress often sees busy phone traffic, it's difficult to compare this year to previous years, argued one Republican Senate aide, given the cross-timing of issue-specific debates with a new administration and a long string of nominations.
"It's going to be an apples to oranges comparison no matter the circumstance," said the aide, who was speaking on background.
Not all calls are from senators' own constituents. In fact, Sen. Susan Collins, R-Maine, estimated 90% of calls to her office recently have been from states other than Maine.
"That's a little bit frustrating because I want to hear from Mainers on these nominations, and we are, but we also have a lot of constituents who are trying to get through with questions about the health care bill that I've introduced and who also need help with casework, like Social Security benefits and VA benefits," Collins told CNN in a statement.
Unsurprisingly, phone lines are jamming up, and some senators have taken to social media to branch out.
"We are experiencing heavy call volumes in all our offices. Staff is answering as many as possible. Please continue calling to get through," Republican Sen. Dean Heller of Nevada tweeted Friday.
Sen. Rob Portman, R-Ohio, put up a message on his homepage
urging visitors who've been unsuccessful with the phones to leave a message online.
And sometimes it's the senators themselves who are urging more people to dial in.
"The last three days have been the BUSIEST IN CAPITOL SWITCHBOARD HISTORY. By almost double. This is working. Keep it up and please RT," tweeted
Sen. Brian Schatz, D-Hawaii.