Washington (CNN) President Donald Trump offered outward optimism Wednesday at his party's electoral successes, a cheeriness that was later belied by surly, combative exchanges with reporters over the dark tone he adopted in the midterms' closing days.

In a post-election news conference, a weary-seeming President ticked through his party's wins, characterizing an expanded majority in the Senate as a history-defying feat of political prowess. He shrugged off new threats from Democrats, who will assume control of the House with new investigative power.

But when the questions started coming, the President's sunny outlook melted away. He lashed out at questions about his fear-mongering and race-baiting rhetoric against immigrants, and demanded a reporter inquiring about voter suppression take her seat.

He went back and forth on his opinion of the newly powerful Democrats, alternately vowing to find areas of cooperation and threatening them with investigations of his own. He vowed a "warlike posture" should he find himself barraged with subpoenas.

"Almost from the time I announced I was going to run, they've been giving us this investigation fatigue," Trump said. "They can play that game, but we can play it better, because we have a thing called the United States Senate, and a lot of very questionable things were done."

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