Sen. Ted Cruz said giving "billions" to Iran is "an exceptionally bad idea."

"Reagan is rolling over in his grave," Cassidy wrote, adding that the deal "is the worst foreign policy blunder in decades."

One GOP Senator described the deal as "the worst foreign policy blunder in decades." Others are privately comparing it to the Obama Iran deal that Trump tore up.

The President's deal with Iran risks

“History demonstrates that sending billions of dollars to theocratic lunatics who want to murder us is a very bad idea," Cruz said.