Photo Illustration by Luis G. Rendon/The Daily Beast/Getty ImagesLast month, Sen. Jon Tester (D-MT) was speaking at a boozy annual Montana fundraiser, known locally as the “Democratic prom,” when he encountered a ritual that has become commonplace for high-profile Democrats these days.Interruption.“I am a Jew! I am a Democrat,” a protester holding a Palestinian flag shouted during Tester’s speech. “You have blood on your hands,” the protester yelled, before sheriff deputies dragged him out of th