US House speaker Paul Ryan has called for the Republican candidate in Montana's congressional election to apologise after allegedly attacking a reporter for The Guardian.
Mr Ryan said the incident involving Greg Gianforte and reporter Ben Jacobs was "wrong and should not happen".
Mr Ryan would not say if Gianforte should be barred from joining the House Republican conference if he wins Thursday's election.
He said: "I'm going to let the people of Montana decide who they want as their representative."
The chairman of the National Republican Congressional Committee, congressman Steve Stivers, also weighed in, saying: "From what I know of Greg Gianforte, this was totally out of character, but we all make mistakes."
Gianforte was charged with misdemeanour assault after grabbing a reporter by the neck and throwing him to the ground.
If convicted, he would face a maximum fine of 500 US dollars or six months in jail.