Sen. Chuck Grassley Charles (Chuck) Ernest GrassleySenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE (R-Iowa) on Thursday disputed President Trump's claim that his proposed tax cuts would be the largest in U.S. history but nonetheless offered support for the president's reform plan.

Trump has repeatedly talked up the size of proposed corporate and income tax cuts. In a speech to the National Association of Manufacturers last month, he said it would be a "giant, beautiful, massive, the biggest ever in our country, tax cut."

But Grassley, a member and former chairman of the tax-writing Senate Finance Committee, took issue with that claim in a series of tweets. Grassley listed the size of tax cuts passed during the George W. Bush administration and then provided estimates of what the size of those cuts are adjusted for inflation.

1/3 @reslDonaldTrump Ur tax cut will not be "largest in history of country" Here are the fact fr my own self Fact Checker — ChuckGrassley (@ChuckGrassley) October 12, 2017

2/3 when I chaired Finance 2001 $1.35T adjusted for inflation =2016 $1.865T in tax cuts 2003 350B=2016 $468B 2005 $70B=2016 $88B — ChuckGrassley (@ChuckGrassley) October 12, 2017

It's unclear exactly how much of a net tax cut will be included in legislation. The Senate Budget Committee approved a measure that would allow up to $1.5 trillion in tax cuts, but Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) has said he won't vote for any tax bill that adds to the deficit. The text of a tax bill won't be released until after the House and Senate agree on a budget resolution.

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Tax legislation is expected to be based on a framework that the White House and congressional GOP leaders released in late September.

The plan would cut the corporate rate from 35 percent to 20 percent and lower the top rate for businesses whose income is taxed through the individual code from 39.6 percent to 25 percent.

On the individual side, the plan would collapse the current seven tax brackets to three, with rates of 12, 25 and 35 percent. However, it also gives Congress an option to propose a fourth tax rate above 35 percent. The top individual rate is currently 39.6 percent.

Grassley praised the framework, arguing that it would help to create jobs.