WASHINGTON — Groups spending millions in anonymous donations are leading the outside efforts to either defend President Trump or sell his agenda with voters and Congress, despite the president’s repeated calls to “drain the swamp” in Washington of special-interest money.

The political empire affiliated with billionaire Charles Koch has spent $2 million to date to advance Trump’s tax-cut blueprint and will hold events this week in Washington to kick off the next phase of its multimillion-dollar campaign to drive congressional support for a comprehensive tax plan to slice corporate tax rates and enact broader tax cuts.

Americans for Prosperity, the Koch network’s grass-roots arm, already has 50 events scheduled in August and September to help promote the tax plan.

The pro-Trump Great America Alliance is spending $450,000 on a TV and digital ad that casts special counsel Robert Mueller’s probe into possible collusion between Russia and Trump’s campaign as a “rigged game.”

The group already has pumped more than $3 million in advertising to advance Trump’s policies and has committed to spending $5 million more, said Eric Beach, a Republican strategist who helps run the group.

The Judicial Crisis Network, which spent $7 million to push Trump’s top judicial nominee, Supreme Court Justice Neil Gorsuch, is “prepared to spend whatever we need to spend to help President Trump fulfill his promise of restoring balance to our federal courts,” policy director Carrie Severino said in a statement.

Trump has more than 100 judicial vacancies to fill.

Another pro-Trump group, America First Policies, has spent $5 million push his agenda and to help a Trump-supported congressional candidate in Georgia.

All operate as nonprofits, can accept unlimited funds from virtually any source but are not required to disclose their donors publicly.

Spending by groups like these in policy and political fights is soaring, following court decisions relaxing corporate and union spending on advertising that targets elected officials.

So far this year, non-profit groups have spent $7.5 million to influence congressional special elections, up from $1.8 million at this point in the 2013-2014 election cycle, according to the nonpartisan Center for Responsive Politics, which tracks political spending. Most of this year's nonprofit election spending — $5.8 million — targeted a June special election in Georgia that became the nation's most expensive House race.

The anonymous donations make it impossible for voters "to consider who's pushing these messages," said Sheila Krumholz of the Center for Responsive Politics.

White House officials said they do not direct the activities of outside groups or coordinate with them. But they said the administration supports the free-speech rights of outside organizations that are acting lawfully.

Trump often has cited the influence of money in politics to criticize others and question their credibility.

On Wednesday, for instance, Trump deployed his “drain the swamp” campaign mantra to target his acting FBI director, Andrew McCabe, on Twitter.

In two tweets, the president asked why Attorney General Jeff Session hasn’t replaced McCabe despite McCabe’s wife getting “big dollars … from Hillary Clinton and her representatives.”

“Drain the Swamp!” he concluded.

At the heart of Trump’s complaints about McCabe: The more than $675,000 that his wife Jill McCabe received during her unsuccessful 2015 campaign for the Virginia state Senate. The money came from the Virginia Democratic Party and the political action committee tied to Virginia Gov. Terry McAuliffe, a close Democratic ally of the Clintons.

Senate Judiciary Chairman Chuck Grassley, R-Iowa, has urged the Justice Department’s inspector general to investigate whether Andrew McCabe should have recused himself from later overseeing the investigation into Hillary Clinton’s use of a private email server.

Fred Wertheimer, president of the ethics watchdog Democracy 21 and a critic of Trump’s decision to retain ownership of his businesses while serving in the White House, said Trump has a pattern of “selectively” picking examples of potential ethics violations “for people he doesn’t like.”

“He then turns around and opens the floodgates for people to buy influence in Washington,” Wertheimer said. “President Trump has been a political fraud on this question of draining the swamp since the day he took office.”

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Democrats also have used nonprofits to advance their political causes. And Trump is not the first president to have an outside organization push his agenda.

During his second term in office, President Obama and his allies transformed his campaign operation into Organizing for America, a non-profit advocacy group. It voluntarily disclosed its donors and, in the face of criticism from watchdog groups, decided to prohibit corporate contributions.

Clinton, Trump's 2016 rival, recently announced the formation of a nonprofit group, Onward Together, to help fund some of the liberal efforts against Trump's policies.

At least two new nonprofit groups have sprung up with the specific goal of advancing Trump’s agenda.

A leading group, America First Policies, has close ties to Trump. Top advisers have included former White House deputy chief of staff Katie Walsh and Brad Parscale, who oversaw the campaign's digital operations.

Erin Montgomery, a spokeswoman for America First, said the group remains focused on policy and takes no direction from the White House on its activities.

But she said the “unfair media coverage” of Trump has “inspired donors to fight” for his agenda.

"We need to remind people of the policies he’s already enacted and all the strong policies that are already coming out of the White House," she said.

Recent ads have included a 30-second spot, called "Shaken," which warns that "the establishment will stop at nothing to take down our president," as images of news anchors, fired FBI director James Comey, House Minority Leader Nancy Pelosi, D-Calif., actress Meryl Streep and other Hollywood critics flash on the screen.

"President Trump is fighting back. Winning for us, not himself. Draining the swamp," a male narrator intones. "We will fight. We will win."

Beach's Great America Alliance, meanwhile, is the outgrowth of a super PAC that raised nearly $28 million to support Trump during the 2016 campaign. He said the nonprofit arm will remain active on Trump's behalf "for the long haul."

Trump "won on an agenda, and it includes taking on special interests, members of the media, the intelligence community," Beach said. Its latest ad, "Witch Hunt," features conservative commentator Tomi Lahren and targets Mueller and other investigators examining the Trump campaign and Russian meddling, raising questions about the independence of their probe.

Other nonprofits actively pushing Trump's agenda have histories that pre-date the real-estate developer's political rise.

Officials in the Koch network, for instance, did not back his candidacy but view his presidency and Republican control of Congress as a rare opportunity to advance their priorities on overhauling the tax code and repealing the 2010 Affordable Care Act.

Similarly, the Judicial Crisis Network (JCN) has worked for years to secure the appointment of conservatives to the federal bench and spent millions to help successfully block the confirmation of Judge Merrick Garland, Obama's pick to replace the late Justice Antonin Scalia.

Like other groups, JCN's leaders cast using anonymous money for its policy fights as a First Amendment matter.

“We are proud to count on supporters who value privacy and freedom of expression," Severino said in a statement.