(CNN)GOP and conservative groups account for the bulk of the more than $13.3 million spent by outside organizations on the special election in Pennsylvania's 18th District, according to Federal Election Commission filings and spending disclosures.
GOP, conservative groups have spent $10 million-plus on the PA-18 special election
Nearly $10.7 million -- about 80% of the outside spending in the district -- has gone to boost Republican candidate Rick Saccone or oppose Democrat Conor Lamb. Conversely, Lamb has benefited from about $2.6 million worth of independent expenditures.
Despite the spending help, Saccone has been locked in a tight contest with Lamb, and actually trailed the Democrat in a Monmouth University poll released the day before the election -- 51% to 45%.
In terms of campaign spending, Lamb's campaign significantly outraised and outspent Saccone's in the race. According to their pre-special election FEC filings, Lamb had raised $3.9 million and spent nearly $3.1 million, while Saccone raised just over $600,000 and spent around $615,000.
The torrent of outside spending has continued unabated in the weeks leading up to election day. Since just March 1, nearly $2.2 million has been spent by outside groups -- about $1.5 million for Saccone, and about $700,000 for Lamb -- on a mix of ad production, ad placement, direct mail, and get-out-the-vote efforts.
Fourteen groups -- seven on the GOP side, and seven on the Democratic side -- have accounted for over 95% of the spending.
For Republicans, the Congressional Leadership Fund -- a Paul Ryan-aligned super PAC -- and the National Republican Campaign Committee have been the largest spenders by far, each accounting for about $3.5 million on the race ($7 million total). The RNC also spent nearly $1.3 million in the district, and two Trump-aligned groups -- America First Action and 45Committee -- spent $1.1 million and $560,000, respectively. The Club for Growth Action Fund, a regular booster of GOP candidates, also spent just over $100,000 on the race and Ending Spending, a conservative super PAC, chipped in $513,000.
Among Democrat-aligned groups, the Democratic Congressional Campaign Committee, Patriot Majority PAC, and the VoteVets.org Action Fund have been the biggest players. The DCCC took an under-the-radar approach to backing Lamb, disclosing only $312,00 in spending, according to FEC filings, but stealthily investing over $1 million in the race over the past 3 months, according to a Democratic source familiar with the strategy. That investment included a $426,000 transfer to the Pennsylvania Democratic Party and additional investments in TV and digital advertising, as well as turnout efforts. Patriot Majority and VoteVets.org both spent around $340,000 on the race.
Supplementing that spending, End Citizens United -- a PAC devoted to curbing the influence of outside money on elections -- spent about $250,000 on Lamb's behalf in late January; the Service Employees International Union Committee on Political Education spent around $112,000; and two PACs, Progressive Turnout Project and Working America, combined to spend almost $100,000 on get-out-the-vote efforts.