Democratic Rep. slams Trump in tweet: 'Lock him up?'

One of President Trump's popular campaign chants is now being used against him amid the controversy over his firing of FBI Director James Comey.

On Thursday night, Representative Hakeem Jeffries of New York tweeted, "Evidence of Trump's effort to obstruct justice continues to emerge. Lock HIM up?"

His comment was a play on the phrase "lock her up" which Trump supporters would shout during the presidential campaign in reference to Hillary Clinton's email controversy.

Click through the craziest reactions to Trump's deleted tweet:

Jeffries also included a link to a New York Times report about a private dinner Trump and Comey had in January where the president allegedly asked for the FBI director's loyalty.

Comey reportedly refused and according to CNN, that is one of the reasons he was fired by Trump.

The president himself has since denied the Times' account on Fox News, telling Jeanine Pirro, "I don't know how it got out there because I didn't ask that question."

However, like Jeffries, other Democrats are alleging that Trump may have broken the law by firing Comey as a way to impede the investigation into Russia.

Senator Dick Durbin said Friday, "President Trump is dangerous because he may be obstructing justice in terms of the investigation that goes to the heart of our democracy, the accountability of the president."

But Harvard law professor Mark Tushnet recently told Vox that Trump "had the authority to fire Comey for any reason whatsoever, including the fact that, as appears to be the case, Comey was pursuing the Russia investigation more vigorously than Trump wanted."

Tushnet speculates that the president may, however, be accused of obstruction of justice if he does not provide accurate information about his financial and other dealings with Russia.