When asked whether she's worried it will hurt her campaign, Warren responded, "This is not about politics."

"Impeachment is something I take very seriously. I take no joy in this. But this is about a constitutional oath that every single member of the Senate took to -- uphold the Constitution of the United States."

To keep her message out on the campaign trail when she can't be, Klobuchar in early December said that she will deploy surrogates to help her campaign while she is in D.C. for her "constitutional duty."

Shannon Beckham, national press secretary for Bennet, said the Colorado senator's "duties, and his responsibility to uphold the Constitution and rule of law, come before any campaign."

Sanders: impeachment 'is what the House has to do, because you have to have standards for the president of the United States. If a president can obstruct justice, if a president, in my view, can violate the emoluments clause and make himself rich because he is president, add additional revenue for his family, if a president can use military ["]aid["] to gain dirt on his opponent, uh, if you allow that to go on, the what kind of standard are you setting for future presidents?"  [KESQ-TV, running time 00:00:47]

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