DENVER (AP) — Facebook founder Mark Zuckerberg and his wife, Priscilla Chan, on Tuesday donated an additional $100 million to helping local election offices prepare for November even as some conservatives are stepping up their efforts to stop the funds from being used.

The contribution brings the total funding for the election from Zuckerberg and Chan to $400 million — the same amount that Congress allocated in March to help fund election offices as they dealt with the difficulties of adapting to new voting behavior during the coronavirus pandemic. Election experts had estimated it could cost $4 billion to make all the changes, but Senate Republicans never acted on a relief bill from the Democratic-controlled House that included $3.6 billion to help voting officials.

Zuckerberg and Chan stepped into the gap initially in September, with a $300 million donation. That came after other donors had already been contributing to the nonprofit that is receiving most of the Facebook founder's contributions, the Chicago-based Center for Technology and Civic Life.

“We’ve seen massive interest in the COVID-19 Response Grant program over the last month from over 2,100 election officials who are seeking funding to ensure safe, health election options for voters in every corner of the country,” said Tiana Epps-Johnson, executive director of the Center for Technology and Civic Life.

The money will pay for protective equipment to prevent spread of the coronavirus at polling sites, drive-thru voting locations, equipment to process mail ballots and more.

The CTCL is respected by election administrators in both parties. But it was founded by former staffers of a Democratic technology firm, and late last week Louisiana's Republican Attorney General, Jeff Landry, moved to block 26 offices in his state from taking $7.8 million in funds. Landry is also working on rewriting state law to bar such arrangements in the future.

A Republican legal group late last week also announced it has filed lawsuits in nine swing states, including Iowa and Pennsylvania, against the donations.

Phill Kline of the Thomas More Society's Amistad Project in a statement last week announcing the litigation called the donations “an insidious, coordinated, and stealth campaign to manipulate this year’s elections.”

Zuckerberg, in a post on Facebook, acknowledged the controversy. “Since our initial donation, there have been multiple lawsuits filed in an attempt to block these funds from being used, based on claims that the organizations receiving donations have a partisan agenda,” Zuckerberg wrote. “That’s false. These funds will serve communities throughout the country -- urban, rural and suburban – and are being allocated by non-partisan organizations.”

Zuckerberg added that most election offices that applied have fewer than 25,000 registered voters in their jurisdictions. Some conservatives have criticized CTCL for donating to election offices in large Democratic-leaning cities in swing states. In a widely circulated video from President Donald Trump's campaign, a campaign worker being expelled from an election office in Philadelphia — the recipient of an $8 million CTCL election grant — asks if it's not a public place “because it's being funded by the nonprofit?”

Zuckerberg added: “I agree with those who say that government should have provided these funds, not private citizens. I hope that for future elections the government provides adequate funding. But absent that funding, I think it’s critical that this urgent need is met.”