The total is more than 40 percent of spending by super PACs, nonprofits and other organizations in the presidential contest since the general election began and is more than any other three-week period in the race.
Since Oct. 29 alone, GOP-aligned outside spending groups outspent their Democratic counterparts in the presidential race $84 million to $20 million, according to a Center for Public Integrity analysis of Federal Election Commission records collected by the Sunlight Foundation.
“Memories are short,” said attorney Dan Backer, whose clients include several conservative outside spenders. “The more you can define the message in the final days, the more likely you are to motivate your base, sway undecided [voters] and turn off supporters of your opponents.”
The outside spending no doubt helped Romney in his fight with his better-funded opponent, President Barack Obama — the Romney campaign reported about $53 million in the bank through Oct. 17 compared with the Obama campaign’s nearly $94 million.
The top spenders during the home stretch were super PACs Restore Our Future, which spent more than $45 million on ads in the presidential contest since Oct. 17 and American Crossroads, which spent $35 million.
Restore Our Future was created by several former Romney aides. American Crossroads was co-founded by GOP strategist Karl Rove.
A study by the Wesleyan Media Project reports nearly 100,000 ads were aired by all political organizations, including campaigns, between Oct. 22 and Oct. 29.
GOP groups dominated the airwaves in Columbus, Dayton, and Toledo, Ohio, as well as Tampa, Fla., the study found. Democratic groups, led by the Obama campaign, enjoyed an edge in Las Vegas, Milwaukee, Norfolk and Roanoke, Va.
Last-minute ads from conservative groups slammed Obama on everything from foreign policy to the economy.
One American Crossroads ad accused the president of “making China stronger and America weaker,” while ads produced by Restore Our Future accused him of “flat-lining” the economy and argued that it could “stay dead” for four more years unless Romney was elected.
Meanwhile, Romney was hit in the final days by ads emphasizing his Medicare proposals and private equity background.
One ad from the pro-Obama super PAC Priorities USA Action, created by two former White House aides, alleged that Romney was “director of a company that stole millions from Medicare” and contended that as president, Romney would “end Medicare as we know it.”
Overall, Priorities USA Action pumped more than $21 million into ads during the final three weeks of the election.
Thanks to changes to campaign finance law in the wake of the U.S. Supreme Court’s 2010 Citizens United ruling and another federal court decision, nonprofits and super PACs are free to collect donations of unlimited size from nearly any source.
Money raised from individuals, corporations and unions is used to pay for advertisements — so long as they are not coordinated with the campaigns they are designed to aid.
The advertising surge included several high-profile U.S. Senate races.
Republicans need a net gain of four seats to wrest control of the Senate away from Democrats.
In Indiana, allies of Richard Mourdock have poured at least $7 million into the race during the past three weeks, according to the Center’s analysis of data from the Sunlight Foundation. That’s about half all money spent by outside groups backing Mourdock during the general election race to date.
Mourdock beat six-term incumbent Sen. Richard Lugar in the primary.
Outside groups supportive of Democratic Rep. Joe Donnelly got a boost after Mourdock said pregnancies arising after a rape were “something God intended to happen” at an Oct. 23 debate.
Pro-Donnelly outside spending groups have spent more than $10 million over the course of the general election and more than $5 million in the final three weeks.
Polls now show Donnelly with a slight lead over Mourdock in the Republican-leaning state.
Not all outside spending has favored Republicans.
During the past three weeks, conservative groups sunk at least $1.8 million into the Missouri race for U.S. Senate, where they hoped to defeat incumbent Democrat, Sen. Claire McCaskill.
McCaskill’s allies spent about $3 million during the same period.
Rep. Todd Akin, her Republican opponent, bucked calls from his own party to drop out of the race after he said women who were victims of “legitimate rape” rarely get pregnant. Many deep-pocketed conservative groups that had been spending in the race directed their resources elsewhere following the comment.
In the final three weeks, outside groups have spent nearly $70 million on advertisements in five hotly contested Senate races — Montana, North Dakota, Ohio, Virginia and Wisconsin.
Conservative groups account for 62 percent of the spending, the analysis found.
The contentious race between Republican George Allen and Democrat Tim Kaine, both former governors, has drawn more than $50 million in outside spending so far with almost $22 million coming in the past three weeks —about $14 million from conservative groups and about $8 million from liberal groups.
Crossroads GPS, the conservative nonprofit sister group of American Crossroads, sought to tie Kaine to Obama, saying both “ran up spending” and endorsed “defense cuts that could kill over 200,000 Virginia jobs,” according to one attack ad.
Meanwhile, VoteVets Action Fund, a Democratic-aligned nonprofit, launched an Oct. 26 ad saying Allen has repeatedly “turned his back” on veterans, a key voting bloc in Virginia.
“If George Allen thinks veterans’ programs are a waste, maybe voting for him is the real waste,” says the David Nasse, a veteran of the wars in Iraq and Afghanistan.
Rachael Marcus contributed to this report.