Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.) on Wednesday congratulated Republicans for being honest that the GOP tax bill was written for wealthy campaign contributors.

"This tax bill was written for Republicans’ wealthy campaign contributors. I want to congratulate my Republican colleagues for their honesty about that," Sanders tweeted Wednesday.

This tax bill was written for Republicans’ wealthy campaign contributors. I want to congratulate my Republican colleagues for their honesty about that. — Bernie Sanders (@SenSanders) December 13, 2017

"There has not been one public hearing, no opportunity to hear from economists, governors, mayors or ordinary Americans who will be impacted by this tax bill. This is a sham," he said in a subsequent tweet.

There has not been one public hearing, no opportunity to hear from economists, governors, mayors or ordinary Americans who will be impacted by this tax bill. This is a sham. pic.twitter.com/YBHBMXkLEN — Bernie Sanders (@SenSanders) December 13, 2017

In a video posted on Twitter, Sanders said that some Republicans have said publicly that if they don't pass this tax bill, their "wealthy friends will stop contributing."

"I appreciate that honesty," he said.

Last month, Sen. Lindsey Graham Lindsey Olin GrahamSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (R-S.C.) said "financial contributions will stop" for the GOP if the party doesn't pass tax reform.

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"The party fractures, most incumbents in 2018 will get a severe primary challenge, a lot of them will probably lose, the base will fracture, the financial contributions will stop, other than that it'll be fine," he said.

Rep. Chris Collins Christopher (Chris) Carl CollinsConspicuous by their absence from the Republican Convention NY Republican Chris Jacobs wins special election to replace Chris Collins 5 things to watch in Tuesday's primaries MORE (R-N.Y.) also acknowledged last month that he is facing pressure from donors to ensure the GOP tax-reform proposal gets done.

Collins last month had been describing the flurry of lobbying from special interests seeking to protect favored tax provisions when a reporter asked if donors are happy with the tax-reform proposal.

“My donors are basically saying, ‘Get it done or don’t ever call me again,’” Collins replied.

On Wednesday, Senate and House Republicans struck an "agreement in principle" on a sweeping tax-cut bill.

GOP sources familiar with the conference committee talks said negotiators are now just cleaning up some of the details on paying for last-minute changes to the bill, which would lower the top individual tax rate to 37 percent and set the corporate tax rate at 21 percent, according to a person briefed on the package.