US Senator Rand Paul has been assaulted at his home in Bowling Green, Kentucky, police and his office say.
The Republican "was blindsided and the victim of an assault" on Friday, a spokeswoman for him was quoted by US media as saying.
The alleged assailant was arrested and "Senator Paul is fine", Kelsey Cooper said, according to The Hill news website.
Rene Boucher, 59, has been charged with assault, police say.
They said the senator suffered a minor injury. It is unclear why he was assaulted.
Mr Paul, seen as representing the Libertarian wing of the Republicans, ran for the party's presidential nomination in the 2016 election but dropped out after a fifth place finish in the Iowa caucuses.
An ophthalmologist, he represents Kentucky in the US Senate and is the son of former Congressman Ron Paul, who ran for president several times.