FBI agents in 2018 gathered over 4,500 tips related to the investigation into then-Judge Brett Kavanaugh but failed to follow up on them, Senate Democrats charged on Thursday. The FBI set up a tip line for Kavanaugh during the Supreme Court justice’s nomination process and received over 4,500 relevant tips, FBI Assistant Director Jill Tyson told senators in a June 30 letter made public this week. However, the FBI appeared to merely pass on the information to the Office of White House Counsel, which had requested an investigation and, later, a supplemental probe. The process rankled Democrat senators, who accused the FBI of being “politically constrained” by the White House under President Donald Trump. “If the FBI was not authorized to or did not follow up on any of the tips that it received from the tip line, it is difficult to understand the point of having a tip line at …