Midterms spending overview: Total expected to reach $5.2 billion

As the U.S. goes through one of the most contentious midterms in recent years, the amount of spending in the 2018 election is setting records -- both in individual races and overall.

Election overview

According to a projection based on the Center for Responsive Politics' analysis of Federal Election Commission reports, the total amount of money spent on congressional races in this election cycle is expected to reach $5.2 billion, a 35 percent increase from the 2014 midterms.

This includes money spent by candidate campaigns, party committees and various outside groups. With a total of 1,661 Democratic House and Senate candidates and 1,471 Republican candidates, so far, a total of $1.26 billion has come from the Democratic side and a little shy of $890 million has come from the Republican side.

More than $1.3 billion in outside spending has come from more than 3,200 outside groups, including party committees, super PACs and political nonprofits, marking a 60 percent increase from 2014.

Most expensive races

Top Senate races:

1. Florida Senate: $181 million ($91 million from candidate campaigns, $90 million from outside groups)
2. Missouri Senate: $119 million ($42 million from candidate campaigns, $77 million from outside groups)
3. Texas Senate: $107 million ($94 million from candidate campaigns, $14 million from outside groups)
4. Indiana Senate: $104 million ($36 million from candidate campaigns, $68 million from outside groups)
5. Arizona Senate: $104 million ($38 million from candidate campaigns, $66 million from outside groups)

In Florida, the Senate race between Democrat Bill Nelson and Republican Rick Scott has brought in more than $181 million. More than $91 million of that has come from the two candidates, with challenger Scott outspending Nelson by more than $40 million. The Democratic leadership has jumped in to back Nelson, with major Democratic outside groups spending more than $53 million in support of Nelson and against Scott. Meanwhile, New Republican PAC, a super PAC almost exclusively dedicated to supporting Scott has spent more than $29.5 million against Nelson.

Democratic Sen. Claire McCaskill's vulnerable seat in Missouri has brought in more than $76 million from outside groups to the Missouri Senate race. Conservative groups led by Senate Leadership Fund, the National Republican Senatorial Committee and Americans for Prosperity, have spent more than $41 million in support of Hawley, while liberal groups have spent more than $35 million in support of McCaskill. Meanwhile, incumbent McCaskill's campaign has outspent Hawley by far, with the vulnerable Democrat spending more than $33 million and the Republican challenger spending $7 million.

Top House races:

1. California's 39th District: $34.5 million ($21 million from candidate campaigns, $14 million from outside groups)
2. California's 48th District: $33 million ($13 million from candidate campaigns, $20 million from outside groups)
3. Washington's 8th District: $30 million ($11 million from candidate campaigns, $19 million from outside groups)
4. New York's 19th District: $29 million ($15 million from candidate campaigns, $13.5 million from outside groups)
5. Pennsylvania's 1st District: $29 million ($15 million from candidate campaigns, $13.5 million from outside groups)

In the lower chamber, a toss-up between two minority candidates in California's 39th Congressional District, where immigrants make up a third of the population, has brought in the most money. Democrat Gil Cisneros' campaign has spent $10.5 million, while Republican Young Kim has spent just about $2 million. Kim has a strong backing of House GOP leadership though, with its super PAC Congressional Leadership PAC boasting a $6.3 million in support of Kim. House Democratic leadership is also behind Cisneros, with House Majority PAC and DCCC spending more than $5.2 million in the race.

GOP Rep. Dana Rohrabacher's effort to defend his seat in California's 48th district has also become increasingly expensive, with candidate campaigns spending nearly $13 million and outside groups pouring in nearly $20 million. The Democratic side is eager to unseat the vulnerable Republican, with challenger Harley Rouda leading an aggressive $6 million campaign, and liberal outside groups including Independence USA PAC, House Majority PAC and DCCC spending more than $11 million to back him. Rohrabacher is backed by Congressional Leadership Fund's $4 million campaign.

Top outside groups

1. Congressional Leadership Fund: $137 million (Super PAC linked to House GOP leadership)
2. Senate Majority PAC: $112 million (Super PAC linked to Senate Democratic leadership)
3. Senate Leadership Fund: $93.5 million (Super PAC linked to Senate GOP leadership)
4. Democratic Congressional Campaign Committee: $84 million
5. National Republican Congressional Committee: $74 million
6. House Majority PAC: $72 million (Super PAC linked to House Democratic leadership)
7. Majority Forward: $46 million (Super PAC linked to Democratic leadership)
8. Independence USA PAC: $37 million (Super PAC funded by Michael Bloomberg)
9. National Republican Senatorial Committee: $33.5 million
10. America First: $31 million (Super PAC linked to Trump campaign manager Brad Parscale)

Top donors

1. Sheldon and Miriam Adelson: $113 million
2. Tom and Kathryn Steyer: $51 million
3. Michael Bloomberg: $50 million
4. Richard and Elizabeth Uihlein: $39 million
5. Donald Sussman: $23 million
6. James and Marilyn Simons: $19 million
7. George Soros: $17 million
8. Steven and Christine Schwartzman: $13 million
9. Fred Eychaner: $12 million
10. Kenneth Griffin: $11 million

An official familiar with Michael Bloomberg's contributions told ABC News that Bloomberg's total investment this cycle will be over $110 million, but only about $50 million of that has been reflected in FEC reports so far.