Hundreds of thousands of people are vowing to protest if President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE fires special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE.

About 300,000 people have now signed up to march in more than 800 events across the country should Trump fire Mueller, The Guardian reported, citing MoveOn. Approximately 20,000 people have signed up in the past two weeks, the newspaper added.

MoveOn, which launched the drive last August, said on its website that Trump's firing of Deputy Attorney General Rod Rosenstein Rod RosensteinDOJ kept investigators from completing probe of Trump ties to Russia: report Five takeaways from final Senate Intel Russia report FBI officials hid copies of Russia probe documents fearing Trump interference: book MORE or Mueller — who is investigating Russia's election interference and possible ties between the Trump campaign and Russia — would create a constitutional crisis.

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"Our response in the hours following a potential power grab will dictate what happens next—whether Congress will stand up to Trump or allow him to move our democracy toward authoritarianism," the site says.

"That's why we're preparing to hold emergency 'Nobody Is Above the Law' rallies around the country, in the event they are needed—800+ of them and counting, in every state, with 300,000 RSVPs to date!"

A report earlier this week said Trump is considering firing Rosenstein after federal investigators raided the office of Trump's personal lawyer, Michael Cohen.

Officials told CNN that the No. 2 Justice Department official, who reportedly personally approved the FBI raid, is Trump's most likely target.

Under DOJ regulations, Rosenstein is the only person with the power to fire Mueller, if he has cause to do so, since Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE recused himself last year.

However, White House press secretary Sarah Huckabee Sanders said earlier this week the president believes he has the power to dismiss Mueller as well.

President Trump on Thursday pushed back against a New York Times report that said he tried to fire Mueller in December, calling the story "fake news from a biased newspaper."