A Republican megadonor on Tuesday threatened to cut off campaign contributions to members of Congress unless they vote for a bill that could effectively ban TikTok in the United States.

“Will never fund any Republican candidates or leadership PACs (or the NRSC) run by Republicans who vote against the TikTok legislation,” venture capitalist Keith Rabois wrote on X.

On Wednesday, the House is expected to pass a bill to force TikTok’s parent company, China-based ByteDance, to sell off the social media platform. Supporters of the bill say ByteDance’s continued ownership of TikTok and its troves of user data pose a national security threat to the United States.

“Support for the TikTok bill is an IQ test” for members of Congress, Rabois wrote in an email to CNBC.

In February, Rabois gave $500,000 to the Congressional Leadership Fund, a political action committee that backs House Republican candidates, according to a Federal Election Commission filing.

Rabois’ threat could have significant sway over those Republican lawmakers still on the fence about whether to support the bill.

For some of the bill’s supporters, that political calculus grew more complicated last week when former President Donald Trump announced he opposed the measure. The presumptive Republican presidential nominee was joined by Tesla CEO and billionaire Elon Musk, who also criticized the legislation.

The bill’s prospects in the Senate were still uncertain on Tuesday.

“On the Senate, it will be up to the Democrat Leader [Chuck Schumer] to bring it to the floor. If he does, we will have a clear voting record” of where each senator stands on the issue, Rabois told CNBC.

If the bill were to pass the Senate and be signed into law, ByteDance would have just six months to sell off TikTok, before the app is banned from American app stores and web hosting sites.

A managing director at Khosla Ventures, Rabois gave just over $41,000 combined last year to the National Republican Senatorial Committee. He also gave over $120,000 to the National Republican Congressional Committee, the NRSC’s House counterpart.

Rabois said that whether or not he continues to support the NRCC will be partly tied to how Republican leadership handles the upcoming vote.

House Speaker Mike Johnson, La., has signaled he plans to vote for the measure and Majority Leader Steve Scalise called it a “critical national security bill.”

Republican Whip Tom Emmer also supports the legislation, and alleged in March 2023 that TikTok was “nothing but a CCP spy app, collecting the sensitive information of 150 million American users which can then be exploited by the Chinese government.”