The reaction to Robert Mueller’s surprise statement on Wednesday highlights a growing schism between 2020 presidential candidates and Democratic leadership on whether to impeach President Donald Trump.

Mueller spoke publicly for the first time on the investigation into Russian interference in the 2016 presidential election and potential obstruction of justice by Trump.

In his statement, Mueller reiterated that his office’s decision not to charge Trump with any crimes did not amount to an exoneration. He cited the Department of Justice’s standing policy that a sitting president cannot be indicted on a federal charges as the reason his office did not consider that option.

But Mueller did allude to impeachment, noting that the Constitution “requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing.”

In response to Mueller’s statement, Democrats emphasized that the power to hold the president accountable resides in Congress.

“Given that Special Counsel Mueller was unable to pursue criminal charges against the President, it falls to Congress to respond to the crimes, lies and other wrongdoing of President Trump,” Rep. Jerry Nadler (D-N.Y.) said in a statement shared on Twitter, adding: “and we will do so.”

House Speaker Nancy Pelosi (D-Calif.) said that Congress would continue to investigate the president and hold him accountable for “his abuse of power,” but did not mention impeachment proceedings.

“The Congress will continue to investigate and legislate to protect our elections and secure our democracy,” she said. “The American people must have the truth.”

But other Democrats, including several candidates for president, have begun to advocate for beginning the impeachment process.

“Mueller leaves no doubt,” wrote Sen. Elizabeth Warren (D-Mass.) on Twitter.

“The Constitution leaves it up to Congress to act—and that’s impeachment,” she concluded.