U.S. President Donald Trump predicted sinking stocks and a reversal of economic gains if House Democrats' impeachment inquiry proceeds.

“If they actually did this the markets would crash,” Trump said in a tweet Thursday morning that cites stock session lows after House Speaker Nancy Pelosi’s impeachment inquiry was announced Tuesday.

Trump said the strong stock market and economy wasn’t “luck” in the tweet, one of more than a dozen sent early Thursday related to impeachment and defending himself against wrongdoing related to a request for Ukraine to investigate a chief 2020 Democratic rival, former Vice-President Joe Biden.

Trump called Democrats’ inquiry the “greatest scam in the history of American politics,” in a separate tweet.

The investigation proceeds Thursday as Acting Director of National Intelligence Joseph Macguire testifies before the House Intelligence Committee on a whistle-blower complaint detailing Trump’s July 25 request to Ukraine President Volodymyr Zelenskiy. A redacted version of that complaint has been declassified and is expected to be released Thursday, according to people familiar with the matter who have asked not to be named to discuss information that’s not yet public.