“Brexit has caused, in my opinion, the lack of trust,” she said.

Brexit is not remotely on the agenda in these elections because councils have power only over local services like trash collection, housing and planning. (One of the points of contention in Colchester is whether the municipality should spend money on a giant sculpture of an elephant.)

Sitting in the kitchen at the home of one of her Conservative colleagues, Ms. Hales recalled that, at the time of the attack, she was taking photos at a beauty spot for a social media post, and some of her campaign material was visible. The obscenity yelled by her assailant included the word “Tory,” the abbreviated name for the Conservatives, Ms. Hales said.

Waiting at the emergency room afterward, she says, she was initially “quite upset thinking, ‘I want to quit.’ ” But after being given the all clear and told to take painkillers, she soon decided she would not be deterred and has since been back out campaigning with her husband.

Darius Laws, the leader of the minority Conservatives on the Colchester Council, says he sees frustration over Brexit all the time, particularly from those angry that the withdrawal deadline of March 29 has been missed and fearful either of a watered-down Brexit or the ultimate betrayal — no Brexit at all.

“The ones who voted Leave hold the doors open, but you almost see them seeing red,” he said.

Outside one home, a sign made partly from ripped-up copies of his campaign literature instructs politicians not to leave leaflets, particularly not Tory ones.

Mr. Laws concedes that Britain’s failures on Brexit have lowered his chances of being re-elected in a very marginal ward, which would dash any hopes of wresting control of the council from Labour.

“We were confident we would be doing that,” he said of ousting Labour. “Now it’s all to play for; it will be about turnout.”