Walker's poll numbers had sunk to dismal levels in the past month following two widely panned debate performances. A new CNN poll Sunday showed Walker receiving less than one-half of 1% from Republican and Republican-leaning voters.
Aides were audibly frustrated with the amount of time Walker got during the last debate, and spent an extended period of time in the media "spin room" after the debate attempting to play down the damage to reporters.
See photos of Walker's 2016 campaign:
Scott Walker on the campaign trail
A former Scott Walker aide fired off a tweetstorm about why Walker dropped out
Republican presidential candidate, Wisconsin Gov. Scott Walker speaks to supporters at Eureka College during a campaign stop, Thursday, Sept. 10, 2015, in Eureka, Ill. (AP Photo/Seth Perlman)
Republican presidential candidate Gov. Scott Walker, R-Wis., waves as he rides the backroads during a two-day motorcycle tour through the nation's earliest presidential primary voting state, Sunday, Sept. 6, 2015, in Washington, N.H. (AP Photo/Jim Cole)
Republican presidential candidate Wisconsin Gov. Scott Walker sits with a plate of brisket at Bill Miller's Bar-B-Q as he waits to do a TV interview during a campaign stop, Wednesday, Sept. 2, 2015, in San Antonio, Texas. (AP Photo/Eric Gay)
DES MOINES, IA - AUGUST 17: Republican presidential candidate and Wisconsin Gov. Scott Walker (L) holds a pork chop at the Iowa Pork Producers Pork Tent during the Iowa State Fair on August 17, 2015 in Des Moines, Iowa. Presidential candidates are addressing attendees at the Iowa State Fair on the Des Moines Register Presidential Soapbox stage and touring the fairgrounds. The State Fair runs through August 23. (Photo by Justin Sullivan/Getty Images)
Wisconsin Governor and Presidential candidate Scott Walker delivers keynote remarks at the DuPage County GOP Summer Reception Thursday, Aug. 13, 2015 at Carlucci's Restaurant in Downers Grove, Ill.(Anthony Souffle/Chicago Tribune/TNS via Getty Images)
WEST ALLIS, WI - AUGUST 12: Wisconsin Governor Scott Walker signs a bill approving financing for a new Milwaukee arena on August 12, 2015 at the Wisconsin State Fair in West Allis, Wisconsin. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this Photograph, user is consenting to the terms and conditions of the Getty Images License Agreement. Mandatory Copyright Notice: Copyright 2015 NBAE (Photo by Gary Dineen/NBAE via Getty Images)
CLEVELAND, OH - AUGUST 06: Republican presidential candidate Wisconsin Gov. Scott Walker fields a question during the first Republican presidential debate hosted by Fox News and Facebook at the Quicken Loans Arena on August 6, 2015 in Cleveland, Ohio. The top ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent political polls. (Photo by Scott Olson/Getty Images)
CHICAGO, IL - JULY 27: Republican presidential hopeful Wisconsin Governor Scott Walker washes down a 'cheezborger' with a Schlitz beer at the famed Billy Goat Tavern during a campaign stop on July 27, 2015 in Chicago, Illinois. Recent polls have Walker leading all Republican contenders in Iowa but trailing businessman Donald Trump and former Florida Governor Jeb Bush in New Hampshire. (Photo by Scott Olson/Getty Images)
Scott Walker, governor of Wisconsin and 2016 Republican presidential candidate, chats with staff as he leaves a campaign stop in Davenport, Iowa, U.S., on Friday, July 17, 2015. Wisconsins top court killed a criminal investigation of Walkers 2012 election campaign, removing a potential stumbling block to his presidential bid. Photographer: Daniel Acker/Bloomberg via Getty Images
Scott Walker, governor of Wisconsin and 2016 Republican presidential candidate, pauses during a campaign stop in Davenport, Iowa, U.S., on Friday, July 17, 2015. Wisconsins top court killed a criminal investigation of Walkers 2012 election campaign, removing a potential stumbling block to his presidential bid. Photographer: Daniel Acker/Bloomberg via Getty Images
DAVENPORT, IA - JULY 17: Republican presidential hopeful Wisconsin Governor Scott Walker steps off a motor home at a campaign event at Modern Woodman Park on July 17, 2015 in Davenport, California. Walker officially announced that he was seeking the Republican nomination for president earlier this week. (Photo by Scott Olson/Getty Images)
LAS VEGAS, NV - JULY 14: U.S. presidential candidate and Wisconsin Gov. Scott Walker speaks at Red Rock Harley-Davidson on July 14, 2015 in Las Vegas, Nevada. Walker launched his campaign on July 13, joining 14 other Republican candidates for the 2016 presidential race. (Photo by Ethan Miller/Getty Images)
Scott Walker, governor of Wisconsin, pauses during his presidential campaign announcement in Waukesha, Wisconsin, U.S., on Monday, July 13, 2015. Walker officially unveiled his White House campaign in the same venue where heÂ celebrated a June 2012 victory as the first U.S. governor to survive a recall election, after successfully confronting organized labor the previous year. Photographer: Luke Sharrett/Bloomberg via Getty Images
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In a now-telling sign, former US Sen. Jim Talent (R-Missouri), a campaign adviser, told Business Insider Wednesday that he was unsure if Walker could win the nomination.
Walker is the second candidate to drop out of the Republican presidential race, following former Texas Gov. Rick Perry, who suspended his campaign earlier this month after he failed to break into the top tier of candidates.