WASHINGTON -- Senate Majority PAC, the super PAC trying to hold the Senate Democratic majority in the 2014 elections, posted a huge fundraising quarter to start the election year with $11 million raised over the first three months of 2014, according to a filing with the Federal Election Commission released on Tuesday.

The super PAC has been the lead backer of Democratic Senate candidates as they have faced expensive attacks from groups linked to the billionaire industrialist Koch brothers. The strong fundraising quarter will no doubt provide funds to play in the key Senate races across the country.

For the entire election cycle, Senate Majority PAC has raised nearly $20 million and spent $8.7 million in eight Senate races, including the special election in Massachusetts last year that elected Sen. Ed Markey (D-Mass.). The group had $8.5 million cash on hand at the end of March.

The strong fundraising by the Democratic super PAC comes as the party's biggest super PAC boosters from the 2012 election have finally come off the sidelines for the midterms. Media magnate and gay rights supporter Fred Eychaner donated $4 million to Senate Majority PAC in the first quarter, and hedge-fund billionaire James Simons gave $2 million.

Labor unions, including those representing teachers, laborers, engineers, autoworkers, public employees, teamsters and pipe-fitters, combined to give $2.55 million in the quarter.

Politicians such as Senate Majority Leader Harry Reid (D-Nev.), Sen. Tim Kaine (D-Va.) and retiring Sen. Jay Rockefeller (D-W.Va.) helped to provide funds. Both Reid and Kaine gave through their leadership PACs -- $100,000 and $50,000, respectively. Rockefeller cut a personal check for $250,000.