Use this interactive to track campaign spending by interest groups and political parties in the 2010 midterm elections. Interest group spending increased dramatically in 2010 following a series of Supreme Court rulings on campaign finance, including the landmark Citizens United v. Federal Election Commission.

Spending by top groups (see full list) :
Group Week before election Two weeks before election Three weeks before election 2010 Total Partisanship
Democratic Congressional Campaign Committee
$24,398,376 $15,462,539 $9,726,970 $63,244,600
100% Democratic
National Republican Congressional Committee
$1,686,074 $10,246,133 $11,945,387 $44,525,486
100% Republican
Democratic Senatorial Campaign Committee
$9,782,093 $7,595,991 $5,191,754 $39,412,938
100% Democratic
American Crossroads
$8,416,112 $8,694,259 $7,278,516 $38,114,259
100% Republican
U.S. Chamber of Commerce
$272,000 $10,499,006 $1,067,266 $31,774,779
93% Republican
National Republican Senatorial Committee
$10,903,145 $6,405,441 $3,599,719 $25,830,910
100% Republican
American Action Network
$2,110,750 $3,564,500 $8,616,182 $15,456,618
100% Republican
American Federation of State County and Municipal Employees
$1,796,103 $2,404,736 $350,928 $11,688,922
100% Democratic
Service Employees International Union
$383,982 $1,033,159 $1,706,012 $9,478,942
100% Democratic
American Future Fund
$356,285 $173,795 $461,885 $9,247,920
100% Republican

Spending in top races (see full list) :
Race, incumbent Week before election Two weeks before election Three weeks before election Total Partisanship
Colo. Sen. Michael F Bennet, D $5,964,300 $7,566,269 $4,878,765 $33,435,827
54% Republican
Pa. Sen. OPEN, Arlen Specter, D $7,009,393 $6,484,877 $3,576,575 $25,006,890
56% Republican
Wash. Sen. Patty Murray, D $4,877,437 $6,749,887 $2,502,141 $18,557,727
56% Republican
Ill. Sen. OPEN, Roland Burris, D $5,598,075 $4,805,430 $2,712,369 $18,059,569
62% Republican
Nev. Sen. Harry Reid, D $3,336,666 $4,786,748 $1,822,714 $16,849,010
59% Republican
Mo. Sen. OPEN, Christopher Kit Bond, R $425,366 $1,641,622 $2,109,775 $12,392,244
59% Republican
Calif. Sen. Barbara Boxer, D $3,942,549 $2,595,559 $242,244 $11,779,256
83% Republican
Ark. Sen. Blanche Lincoln, D $73,697 $91,118 $61,214 $11,749,014
89% Democratic
W.Va. Sen. OPEN, Carte Goodwin, D $2,446,084 $2,791,182 $1,913,011 $10,346,409
54% Republican
Ky. Sen. OPEN, Jim Bunning, R $1,727,581 $2,691,439 $1,247,861 $8,639,509
71% Republican
SOURCES: Federal Election Commission filings; Washington Post research

NOTE: Totals represent spending in calendar year 2010 and will change as new filings are made or information is amended. Data includes "electioneering communication" and electronically-filed "independent expenditure" spending reported to the Federal Election Commission. Spending on "issue ads" targeting candidates will not be included if it is more than 30 days before a primary or more than 60 days before the general election. "Weeks on list" shows the total number of weeks that a group or race has been in the top ten throughout the year.

By T.W. Farnam and Nathaniel Vaughn Kelso -- The Washington Post