Presidential candidate Mike Bloomberg will donate $10 million Thursday to defend vulnerable Democratic House members against paid Republican attacks on their support for impeachment proceedings against President Trump.

The money, which is meant to even an arms race on the 2020 congressional battlefield, was cheered by House Speaker Nancy Pelosi (D-Calif.), who has been fielding concerns from some of her members over a costly Republican advertising offensive as the House moves toward an impeachment vote next week.

“In 2018, Mayor Bloomberg was a critical ally in helping House Democrats regain the majority,” Pelosi said in a statement. “Now, the stakes are even higher as we work to make health care more affordable by reducing the skyrocketing cost of prescription drugs, increase wages and root out corruption. We welcome and thank Mayor Bloomberg for his support.”

In addition to ads by the Republican National Committee and Trump’s reelection campaign, The Washington Post reported Saturday, two Republican groups have committed about $10 million to attack Democratic members of Congress in their districts for embracing what one spot calls the “impeachment charade” in lieu of other legislative priorities.

Up to now, the Democratic response had been led by House Majority Forward, a group with close ties to Pelosi, which ran $1.5 million in television ads promoting the accomplishments of 11 Democratic lawmakers in October.

Decisions about the targeting and messaging made possible by Bloomberg’s donation will be handled by House Majority PAC, the primary Democratic outside group for House races. In 2018, Bloomberg spent more than $100 million to help elect Democrats in the midterm elections, mostly through his own group, Independence USA PAC, which focused on House races.

The new donation is just the latest salvo in an unprecedented political spending spree by Bloomberg, the billionaire former New York mayor who announced his presidential campaign last month and has said he considers Trump “an existential threat.”

Now polling in fifth place nationally, with about 5 percent support among Democratic voters, he is seeking to turn his willingness to spend from his own $55 billion net worth into a selling point for his candidacy in a party that is focused on finding ways of pushing Trump from power.

Over the past month, Bloomberg has spent more than $100 million on ads promoting his campaign message while promising $100 million for anti-Trump digital ads in six swing states during the primaries and $15 million or more for Democratic voter registration efforts before the 2020 election. His campaign now employs hundreds of staff members, and he is hiring field operatives in 27 states.

“Sadly Republicans are more interested in protecting the president than the Constitution,” Bloomberg, who supports impeaching Trump, said in a statement. “Fortunately House Democrats are holding the President accountable, and they need resources to stay in office.”

Robby Mook, a former presidential campaign manager for Hillary Clinton who now runs House Majority PAC, indicated that the money would be used to rebut the Republican talking point that Democrats are no longer focused on kitchen table issues for voters in their districts.

Democrats have passed hundreds of bills on issues such as health care and gun control, but those have largely been tabled in the Republican-led Senate, as Trump and others in his party have publicly excoriated the House for doing nothing.

“With this extraordinary commitment from Mayor Bloomberg, we’ll be able to generate more resources to ensure voters understand how their Democratic House majority is working on the issues that matter, like protecting access to affordable health care and reducing the cost of prescription drugs,” Mook said.

American Action Network, the main politically active nonprofit supporting House Republicans, has launched a $7 million television and digital advocacy campaign aimed at 37 key congressional districts. A separate nonprofit that supports Trump, America First Policies, has committed $3.3 million since October.

Trump campaign manager Brad Parscale tweeted internal polling last week that he said showed impeachment was unpopular in recently won Democratic districts in Oklahoma and New York.

“Impeachment is killing her freshman members,” Parscale wrote. “Say goodbye to your majority, Nancy!”

Nationwide, however, support for impeachment has held steady in recent weeks, despite frequent Republican claims otherwise.

A Washington Post average of polls since the hearings began Nov. 13 finds 47 percent of the country supports Trump’s impeachment and removal from office, while 44 percent opposes the move.

Michelle Ye Hee Lee and Anu Narayanswamy contributed to this report.