Big-money donors have flooded Colorado's Democratic Senate primary.

John Walsh, a former federal attorney, has touted his grassroots support in his bid to unseat Republican senator Cory Gardner, but 70 percent of his campaign funds have come from big-money donors, FEC filings show. More than $540,000 of Walsh's $776,999.12 raised to date came from donors contributing at least $1,000. More than $330,000—43 percent of his cash to date—came from $2,800 contributions, the maximum allowed under federal law.

Walsh's reliance on big-money donors has not softened his rhetoric against money's influence in politics.

In a July video thanking his "grassroots supporters," Walsh called fundraising an "unfortunate" political necessity. He expressed disdain for campaigns that focus on "the most wealthy Americans."

"A huge part of the job of a political candidate is, really unfortunately, raising money," Walsh said. "It doesn't say anything good about our political system that money has such a big influence on political campaigns, but it's a fact of life.

"The only way that we’re going to really restore the way our democracy works is that that fundraising is not to the most wealthy Americans, but rather with the folks who are actually affected by the way the government works," Walsh said.

Walsh served as U.S. Attorney for Colorado under former President Barack Obama before joining mega-firm WilmerHale as a partner in 2017. Though he left the firm to run for office, Walsh's connections to wealthy attorneys have proven vital to his campaign.

Walsh's second quarter FEC filing shows that attorneys have given his campaign $300,000, including a number of contributions from former colleagues at WilmerHale.

Ranked the most liberal out of the twenty most prestigious law firms in the country in a 2016 Harvard study, WilmerHale is known for its connections to the federal government. Robert Mueller spent three years at WilmerHale before becoming special counsel, earning nearly $3.5 million in the process.

Jamie Gorelick, a partner at WilmerHale since 2003, gave the maximum $2,800 to Walsh.

Gorelick previously served in the Clinton administration's Justice Department before making tens of millions of dollars underwriting subprime mortgages at Fannie Mae. A former lobbyist, Gorelick has represented clients such as BP, Google, and J.P. Morgan.

Walsh has previously criticized Republican incumbent Cory Gardner for taking money from lobbyists.

In order to take on Gardner in the 2020 general election, Walsh will have to emerge from a crowded primary field. He is not the only candidate benefitting from big-money donors.

Former Democratic presidential candidate John Hickenlooper officially announced his candidacy Thursday. More than half of Hickenlooper's second quarter presidential fundraising came from supporters giving more than $1,000.

Mike Johnston, a former Colorado state senator, has raised more to date than Hickenlooper raised in his brief presidential run. About 60 percent of Johnston’s second quarter fundraising came from maximum contribution; 85 percent of his cash haul came from those contributing more than $1,000.

Dan Baer, a former State Department official under Obama, raised 54 percent of his $1.3 million war chest from donors contributing more than $1,000.

None of the candidates responded to requests for comment.