BOZEMAN, Mont. — A Republican congressional candidate in Montana charged with shoving a reporter to the ground on the eve of a special election kept a low profile Thursday even as supporters prepared a hotel ballroom for a possible victory party.

Greg Gianforte was charged with misdemeanor assault after witnesses said he grabbed a reporter by the neck on Wednesday and threw him to the ground at Gianforte’s campaign headquarters in Bozeman.

Gianforte, a millionaire tech entrepreneur who has aligned himself with President Donald Trump, said the reporter was being aggressive and grabbed him by the wrist at his campaign office.

The altercation occurred hours before voters went to the polls to decide whether Gianforte or Democrat Rob Quist will fill the U.S. House seat vacated by Ryan Zinke, a Republican who is now Trump’s Interior secretary.

Many see the closely watched election as a referendum on the policies and practices of Trump.