(CNN) What you most hear from congressional Republicans on impeachment this week is the sound of silence.

GOP sources tell CNN they have a good reason for that fear. They have no idea what else House Democrats' investigation will uncover or what comes next.

Along with that fear is frustration with President Donald Trump: his ranting in performances full of false claims , like Wednesday in the Oval Office and White House East Room, and stream of consciousness rapid-fire tweets -- curse words and all -- are not exactly an anti-impeachment road map for his fellow Republicans.

"He is taking it upon himself to tweet about every shiny object," a source involved in Senate GOP discussions tells CNN. "That is not helpful right now."

And although phrases like "witch hunt" and "hoax" worked for the President politically during the investigation by special counsel Robert Mueller, concerned GOP sources -- more than half a dozen, including some in leadership who are talking to and hearing from the rank and file -- tell CNN that they worry the President isn't comprehending what they believe to be true, that this is different.

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