Now, Capuano is facing his first-ever primary challenge — and he’s not alone, with a small but growing number of entrenched Democrats watching as insurgents out-fundraise them with a sense of urgency fueled by President Donald Trump and an unwillingness to follow the old rules of deference to party elders.

Just as the Tea Party revolution culled some deadwood Republicans on its way to retaking the House, an anti-Trump wave may wash out some of the Democrats’ longest-serving members.

“I understand that this is uncomfortable for many people,” said Ayanna Pressley, Capuano’s challenger. “These are different times and it requires our being disruptive.”