Meet the people who write the biggest checks in federal elections

Led by former New York Mayor Michael Bloomberg, America's political megadonors have plowed $3.4 billion into federal contests between January 2009 and December 2020, according to the report by Issue One.

Bloomberg catapulted to the top of the list after spending more than $1 billion on his failed 2020 bid for the Democratic presidential nomination. In the No. 2 spot: Tom Steyer, another billionaire who also ran unsuccessfully for the presidency last year.

Issue One, which works to reduce the influence of money in politics, used data compiled by the nonpartisan Center for Responsive Politics, to unearth the biggest political donors in the six election cycles since the Supreme Court paved the way for unlimited spending in politics with its Citizens United decision.

Issue One CEO Nick Penniman said the figures highlight "the alarming influence of just a handful of wealthy megadonors in our political system."

"Our government can't be responsive to all Americans if our elected officials are beholden to the elite donor class," he said in a statement.

The top contributors are all White and at least eight are billionaires, the researchers concluded. Six of the megadonors mostly supported Democrats; the other six, Republicans.

Their money went directly to candidates, political parties and outside organizations such as super PACs, which can spend unlimited amounts to influence elections but are barred from coordinating their spending decisions with the candidates they support.

Here's the full megadonors list and the amounts they contributed:

Michael Bloomberg, $1.4 billion. The media and financial information billionaire spent $1.09 billion on his 2020 presidential bid before dropping out of the Democratic primary.

Tom Steyer and Kat Taylor, $653 million. Steyer, a California Democrat who became a billionaire running his own hedge fund, already was a big political donor before plowing millions into his own short-lived bid for the presidency in last year's election.

Sheldon and Miriam Adelson, $523 million. Sheldon Adelson, a casino magnate who died in January, was one of the biggest political benefactors in Republican politics. His widow Miriam, a physician, is a political player in her own right with a net worth of more than $37 billion, according to Forbes.

Richard and Elizabeth Uihlein, $138 million. This conservative Illinois-based couple own Uline Corp., a shipping and packaging company.

Ken Griffin, $107 million. The billionaire owner of hedge fund Citadel has backed Republicans.

Donald Sussman, $98 million. This hedge funder is a longtime backer of Democratic candidates and causes.

Jim and Marilyn Simons, $93 million. Jim Simons is the billionaire founder of the New York-based Renaissance Technologies hedge fund. His and wife are stalwart funders of Democratic groups.

Fred Eychaner, $92 million. This Chicago businessman is a longtime funder of Democratic organizations.

Dustin Moskovitz and Cari Tuna, $83 million. Moskovitz is a Facebook co-founder. He and his wife have supported Democratic super PACs.

Timothy and Patricia Mellon, $70 million. Wyoming-based Timothy Mellon, an heir to the Mellon family fortune, emerged in politics as a major donor to a super PAC backing then-President Donald Trump's reelection.

Joe and Marlene Ricketts, $66 million. Republican Joe Ricketts is the founder of TD Ameritrade. Members of the Ricketts family own the Chicago Cubs.

Paul Singer, $63 million. This hedge fund billionaire has helped fund an array of super PACs working to elect Republicans over the years; he also spent heavily to encourage Republicans to back gay marriage.