Washington (CNN) He's loomed -- mostly unseen -- over all but a few months of President Donald Trump's tenure. On Wednesday, former special counsel Robert Mueller moves from the wings to center stage, occupying a spotlight the President would prefer just fade.

Trump has spent the last several days on the phone and in conversation with aides and allies discussing Mueller's upcoming testimony, CNN has learned. Instead of anxiety, the President has expressed irritation at having to watch the man who has shadowed his presidency sit down before two congressional committees Wednesday.

Trump has been quizzing people around him about what they expect while complaining that Democrats will never let the Russia investigation go.

He bemoaned the "Russian witch hunt" a day ahead of the former special counsel's testimony, asking an audience of conservative youth "should I talk about it for a sec" before laying into the probe.

"First of all, it's very bad for our country," Trump said. "It makes it very hard to deal with Russia. We should be able to. They're a nuclear power. They have a big country. And we should be able to deal with them without having this artificial stuff."

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