Wisconsin Gov. Scott Walker is set to drop out of the presidential race Monday night, a source close to the campaign confirms to NBC News.
He is scheduled to hold a press conference in Madison, Wisconsin, at 6 p.m. ET to announce his exit from the race.
The Republican was once considered a frontrunner for the GOP nomination, topping polls in Iowa and winning accolades from conservatives for his fights against labor unions during his tenure as governor of the state.
But a series of missteps -- and the rise of unconventional candidates like Donald Trump and Dr. Ben Carson -- found him plummeting in national and key early state polls.
A CNN/ORC poll out this weekend found Walker winning support from less than one-half of one percent of GOP primary voters.
Walker's performance was lackluster in the two GOP primary debates to date, and he had faced calls to shake up his campaign staff.
He is the second Republican candidate to exit the presidential race. Texas Gov. Rick Perry dropped out before last week's CNN debate in Simi Valley, California.