Sen. Elizabeth Warren (D-Mass.) has a plan to crack down on lobbying in Washington: She wants to institute a progressive tax on “excessive” lobbying expenditures.

The proposal from the 2020 Democratic presidential candidate was first listed among her proposals to rein in Washington lobbying in September, but she is now providing extensive details.

She would place a 35% tax on annual lobbying expenses above $500,000 for corporations and trade organizations. The tax rate will increase to 60% for expenses over $1 million and then 75% for spending exceeding $5 million.

The income generated by the new tax will be placed in a “Lobbying Defense Trust” that will be used to help fund congressional support agencies, such as a reinstated Office of Technology Assessment and the Congressional Budget Office, and heavily lobbied executive branch agencies. It would also create an Office of the Public Advocate to help regular people better influence government decision-making.

The general idea is that a tax on lobbying creates a market-based mechanism to discourage corporate spending that seeks to gain from making back-room deals rather than creating wealth. Currently, there is a strong incentive for corporations and other special interests to spend heavily on lobbying to obtain beneficial treatment. All combined, more than $3 billion was spent on reported lobbying expenditures in each of the past 10 years. Corporations make up the largest share of this spending.

Total revenue from the proposed lobbying tax would have raised $10 billion over the past 10 years, according to an analysis provided by the Warren campaign.

Fifty-one corporations would have been hit with the highest proposed tax rate of 75% for spending above $5 million. These companies and trade groups include the U.S. Chamber of Commerce, Koch Industries, Exxon, Boeing, Microsoft, Pfizer, Walmart, Google and Facebook.