A man has been arrested after allegedly driving a van into a tent where Republican volunteers were registering voters.
The vehicle narrowly missed six volunteers at a stall outside a shopping centre in Jacksonville, Florida.
Gregory Timm, 27, has been arrested and charged with two counts of aggravated assault on a person aged 65 or older, and with criminal mischief and driving with a suspended licence.
Donald Trump issued a warning following the incident, tweeting: "Law Enforcement has been notified. Be careful tough guys who you play with!"
One of the volunteers, Mark Alfieri, told WCAX3: "Out of the blue, a man approached us in a van, was waving at us, kind of a friendly demeanour, thought he was coming up to talk to us.
"Instead, he accelerated his vehicle and ploughed right into our tent, our tables."
Mr Alfieri said the driver then stopped the van, got out and started filming the scene, before making an obscene gesture and driving off.
The mayor of Jacksonville, Lenny Curry, tweeted: "The hate is toxic and dangerous.
"Thankfully no one was injured but certainly they are shaken after being targeted because they were registering voters."
The Duval County GOP said in a Facebook statement that it believed its members were deliberately targeted.
The local Democratic Party condemned the attack, saying: "No one's life should be placed in danger for exercising their first amendment rights. As Democrats, but more importantly, as residents of this great city of Jacksonville, we call on our fellow citizens to act with dignity, civility and respect for one another during this election cycle and beyond."
