“Five hundred [calls] yesterday, and right now, they’re just ringing non-stop,” said an upset staffer at the office of Mississippi Republican Sen. Roger Wicker, who has voted on both sides of the dispute.

Protestors have sent “hundreds or thousands” of calls to Ohio Republican Sen. Robert Portman’s Republican office, a staff member told The Daily Caller.

“That vast majority of calls today have been on that… [and] we’ve been getting calls on that for a couple of weeks,” said a staffer working for Pennsylvania Democrat Sen. Robert Casey.

The calls have stiffened the spine of GOP Senators who might otherwise bend to pressure from business groups and from influential people in their home state, such as editorial writers and clerics, said Roy Beck, executive director of NumbersUSA, which provides a free phone service for Americans who oppose the massive rewrite.

“Our lines sent in hundreds of thousands of calls in the last month,” said Beck.