“What Robert Mueller basically did was return an impeachment referral. Now it is up to Congress to hold this president accountable. We need to start impeachment proceedings. It’s our constitutional obligation.”

That’s what Sen. Kamala Harris (D-CA) said on Twitter shortly after former special counsel Robert Mueller once again said his office did not find sufficient evidence to charge President Trump with collusion or obstruction of justice.

What Robert Mueller basically did was return an impeachment referral. Now it is up to Congress to hold this president accountable. We need to start impeachment proceedings. It's our constitutional obligation. — Kamala Harris (@KamalaHarris) May 29, 2019

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Harris, running for the 2020 Democratic nomination, is polling in the low single digits. Her new call for impeachment proceedings are sure to grab some headlines.

Same for Sen. Elizabeth Warren (D-MA). She’s getting almost no press as the two dozen candidates jockeying for coverage. So, predictably, Warren, too, is pushing for more hearings and impeachment — even though the top prosecutors in America couldn’t find enough to press criminal charges.

“Mueller leaves no doubt: 1) He didn’t exonerate the president because there is evidence he committed crimes. 2) Justice Department policy prevented him from charging the president with any crimes. 3) The Constitution leaves it up to Congress to act—and that’s impeachment,” Warren wrote on Twitter.

Mueller leaves no doubt:

1) He didn't exonerate the president because there is evidence he committed crimes.

2) Justice Department policy prevented him from charging the president with any crimes.

3) The Constitution leaves it up to Congress to act—and that's impeachment. — Elizabeth Warren (@ewarren) May 29, 2019

Sen. Cory Booker (D-NJ) — another candidate polling in single digits — also trotted out the “I” word.

“This Administration has continued to stonewall Congress’s oversight. Beginning impeachment proceedings is the only path forward,” he wrote on Twitter.

This Administration has continued to stonewall Congress’s oversight. Beginning impeachment proceedings is the only path forward. — Cory Booker (@CoryBooker) May 29, 2019

Former Texas Rep. Robert “Beto” O’Rourke — whose campaign has crumbled after a strong opening — also sought the headlines by calling for impeachment.

“There must be consequences, accountability, and justice. The only way to ensure that is to begin impeachment proceedings,” he wrote on Twitter.

There must be consequences, accountability, and justice. The only way to ensure that is to begin impeachment proceedings. — Beto O'Rourke (@BetoORourke) May 29, 2019

Frontrunners Joe Biden and Sen. Bernie Sanders, though, steered clear of the impeachment talk and at press time had not commented on Mueller’s statement.