Story highlights President Trump and the GOP want to end a law blocking churches from operating directly in politics

A final version is being negotiated behind closed doors

(CNN) As Congress debates a provision that critics warn could allow for tax deductible secret political donations, a key Republican senator at the center of the negotiations told CNN he does not want taxpayers "subsidizing" political speech.

The debate weighs around a proposed rule change to the Johnson Amendment, a law that currently prevents nonprofit 501(c)(3) groups from directly participating in politics.

The House tax plan included a rollback of the amendment, a change that non-profit and campaign finance experts warn could lead to an explosion of tax deductible "dark money" political donations funneled through charities. The Senate bill did not include the rule change, which means the matter will be on the agenda of the conference committee this week.

Sen. Orrin Hatch, R-Utah, chairman of the Senate Finance Committee and one of the lawmakers working on the final bill, said the "voice of the nation's faithful" should not be "censored."

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