Check Out the Most Expensive House and Senate Races

Elections are getting more expensive by the year.

The 2014 congressional elections, though seemingly less intense and animated than their recent, wave-election predecessors in 2006 and 2010, are on pace to cost more than any midterm elections ever.

The 2014 House and Senate races will cost at least $3.67 billion, more than the $2.9 billion spent on House and Senate races in 2006 and slightly edging the $3.6 billion spent in 2010, but ranking just below the $3.7 billion spent on congressional races in the presidential-election year of 2012, the Center for Responsive Politics estimates.

What's Behind the 2014 Midterm Election Cycle's Trendiest Attack Line

Kentucky Political Mailer Speaks Volumes on Lack of Data Security Knowledge

Clinton socks away money for general election

The real number will likely be higher. Because of gaps in disclosure requirements, nonprofit groups like the conservative, Koch-backed Americans for Prosperity were able to spend money on "issue ads," which didn't directly tell voters to support or oppose a candidate, for most of the year without reporting them to federal campaign-finance regulators.

The Center for Responsive Politics estimates that "well over" $100 million in 2014 will have gone undisclosed, not counting toward that $3.67 billion total.

So where's all this money going? Here are the most expensive House and Senate races, as compiled by the center. As campaigns and outside groups hurriedly file disclosure reports between now and Election Day, these numbers will change, so check this page for a running list.

MOST EXPENSIVE SENATE RACES

1. North Carolina - Tillis (R) vs. Hagan (D) - $113M

2. Colorado - Gardner (R) vs. Udall (D) - $94M

3. Iowa - Ernst (R) vs. Braley (D) - $82M

4. Kentucky - McConnell (R) vs. Grimes (D) - $78M

5. Georgia - Perdue (R) vs. Nunn (D) - $65M

6. Arkansas - Cotton (R) vs. Pryor (D) - $58M

7. Alaska - Sullivan (R) vs. Begich (D) - $58M

8. New Hampshire - Brown (R) vs. Shaheen (D) - $47M

9. Michigan - Land (R) vs. Peters (D) - $47M

10. Louisiana - Cassidy (R) vs. Landrieu (D) - $42M

Source: OpenSecrets.org/Center for Responsive Politics

MOST EXPENSIVE HOUSE RACES

1. CA07 - Ose (R) vs. Bera (D) - $21M

2. OH08 - Boehner (R) vs. Poetter (D) - $17M

3. CO06 - Coffman (R) vs. Romanoff (D) - $17M

4. AZ01 - Tobin (R) vs. Kirkpatrick - $17M

5. AZ02 - McSally (R) vs. Barber (D) - $16M

6. L10 - Dold (R) vs. Schneider (D) - $16M

7. MN08 - Mills (R) vs. Nolan (D) - $15M

8. NY01 - Zeldin (R) vs. Bishop (D) - $15M

9. FL13 (March special election) - Jolly (R) vs. Sink (D) - $14M

10. FL02 - MacArthur (R) vs. Belgard (D) - $14M

Source: OpenSecrets.org/Center for Responsive Politics

Get real-time results pushed to your phone on Election Night. Click here to sign up for the races that matter most to you.