-- Trump describes election results as win for Republicans

-- Democrats will control House for first time in eight years

-- Republicans consolidate hold on Senate

-- Political gridlock looms with split power in Congress

US Attorney General Jeff Sessions was fired by Donald Trump Wednesday, casting a cloud over the Russia investigation that has dogged the White House, a day after Republicans lost control over the lower house of Congress.

The move capped more than a year of bitter criticism by the president over his legal advisor's decision to recuse himself from the probe into Russian interference in the 2016 election, paving the way for the appointment of Special Counsel Robert Mueller.

In announcing the resignation in a tweet that thanked the former Alabama senator "for his service" -- Trump right away named as acting attorney general Sessions' chief of staff Matthew Whitaker.

That set off immediate alarm bells: Whitaker has been overtly critical of the broad scope granted to Mueller's team to probe beyond allegations Trump's campaign colluded with Russia in 2016, into other ties between Trump, his family and aides, and Russia -- an investigation the president calls a "witch hunt."

In an op-ed in August last year he publicly urged Deputy Attorney General Rod Rosenstein -- who oversees the probe -- to "limit the scope of his investigation to the four corners of the order appointing him special counsel."

As acting attorney general, Whitaker now has the power to wrest oversight away from Rosenstein, and take charge himself.

Democratic Senate Minority Leader Chuck Schumer immediately called on Whitaker to recuse himself from the probe as his predecessor had.

Sessions was the first casualty of a cabinet shakeup that had been expected from Trump following the midterm elections. Sessions was the first US senator to back Trump's presidential run in 2016, giving the New York real estate billionaire credibility against a broad field of Republican stalwarts. The two were reportedly brought together by a shared wish to crack down on immigration.