U.S. President Donald Trump is warning House Democrats against spending the remaining years of his presidency investigating him and the administration.

At a post-midterms news conference Wednesday, Trump declared that Republicans will respond in kind if House Democrats flood his administration with subpoenas to seek his tax returns and investigate his business dealings, his cabinet's conduct and his campaign's ties to Russia. He added that Democrats have "nothing, zero" on him.

"They can play that game, but we can play it better. Because we have a thing called the United States Senate," Trump said. "If that happens, then we're going to do the same thing, and government would come to a halt, and we're going to blame them."

Trump warns House Democrats about trying to investigate him:

Donald Trump says people are tired of all the investigation talk and warns what will happen if Democrats pursue probes in Congress 0:49

The warning came minutes after Trump praised Democratic House leader Nancy Pelosi for her role in the Democrats' successes yesterday and said he hoped the two parties could work together on a number of issues, including economic growth, infrastructure, trade, and lowering cost of prescription drugs.

Trump said House Democratic leader Nancy Pelosi deserves to be House Speaker, and said he wanted to work together with her on a range of issues. (Al Drago/Reuters )

In a news conference shortly after Trump spoke, Pelosi said Democrats will have a "responsibility for oversight" when they take charge in the House in January, but she said committee requests for documents or hearings won't be "scattershot."

Sessions out

During his almost 90-minute session with reporters, Trump sidestepped questions about possible staffing changes in his West Wing or cabinet — including the fate of embattled Attorney General Jeff Sessions — but hinted that moves could be coming soon.

A little over an hour later, Trump tweeted that Sessions was gone.

....We thank Attorney General Jeff Sessions for his service, and wish him well! A permanent replacement will be nominated at a later date. —@realDonaldTrump

Sessions's resignation came after months of personal insults and criticisms from Trump over his recusal from the investigation into potential coordination between Russia and the Trump campaign.

Trump blamed the decision for opening the door to the appointment of special counsel Robert Mueller, who took over the Russia investigation and began examining whether Trump's hectoring of Sessions was part of a broader effort to obstruct justice.

Sessions's chief of staff Matt Whitaker will become the new acting attorney general.

Attacks on media

The president repeatedly became irritated while taking questions from the media, insulting several reporters by name. Trump got particularly angry at CNN's Jim Acosta, when the journalist asked Trump why he was calling the caravan of migrants an "invasion." When Acosta tried to follow up with another question, Trump said, "That's enough!" and a White House aide unsuccessfully tried to grab the microphone from Acosta.

Later Wednesday evening, White House press secretary Sarah Sanders released a statement saying Acosta's press pass was suspended. She accused Acosta of "placing his hands on a young woman just trying to do her job as a White House intern," calling it "absolutely unacceptable."

Watch the exchange in question between Trump and Acosta:

The White House suspended CNN reporter Jim Acosta's press pass after accusing him of "placing his hands on a young woman just trying to do her job as a White House intern" during an exchange with Trump. 0:34

Trump also ordered some reporters to sit down and he deemed one inquiry "racist."

I'm simply asking the questions the public wants to know. <a href="https://t.co/bZ1cZVBKhd">https://t.co/bZ1cZVBKhd</a> —@Yamiche

Trump faces the prospect, starting early next year, of endless investigations after Democrats formally take control of the House, along with stymied policy efforts and fresh questions about the resilience of his unorthodox political coalition. Still, he celebrated Republicans' success in retaining the Senate.

"I thought it was very close to complete victory," he said.

Truce with Trudeau?

Trump was also asked about whether he has "repaired" his relationship with Prime Minister Justin Trudeau since the U.S., Canada and Mexico reached a new trade deal.

"Yes, I have." he said. "We have a very good relationship."

Deep tensions remain

Widely viewed as a referendum on Trump's presidency, Tuesday's results offered a split decision that revealed deep tensions in the American electorate — a rift that could easily widen during two years of divided control of Congress. Trump's aggressive campaign blitz, which paid off in some key victories, suggests he is likely to continue leaning into the fray.

Control of the House gives Democrats the ability to launch investigations into the president and stifle his agenda, but White House aides called on them to reach across the aisle.

"I don't know that there will be much of an appetite for Democrat lawmakers to spend all of their time, or most of their time or even a fraction of their time investigating, instigating, trying to impeach and subpoena people," said Trump adviser Kellyanne Conway.

The president telephoned Pelosi Tuesday night, a conversation that her office said included congratulations and a nod to her pitch for bipartisanship. He said today she deserves to be House speaker.

"I give her a lot of credit. She works very hard and she's worked long and hard. I give her a great deal of credit for what she's done and what she's accomplished," Trump said.

Trump speaks during a news conference in the East Room at the White House in Washington, Wednesday, Nov. 7, 2018. (Manuel Balce Ceneta/Associated Press)

In addition to his conversation with Pelosi, Trump called Republican Senate majority leader Mitch McConnell, Republican House Speaker Paul Ryan and Senate minority leader Chuck Schumer, as well as other candidates he backed during the race, the White House said. And he downplayed reports of voter irregularity and suppression, particularly in Georgia, instead saying, "I heard it was very efficient in Georgia."

Trump had aggressively campaigned in the closing days of the race, his focus on boosting Republicans in states he carried in 2016.

In the three races he targeted on the final day, Trump's picks won Tuesday night, with Republican Mike Braun defeating Democratic Sen. Joe Donnelly in Indiana, Republican Josh Hawley defeating Democratic Sen. Claire McCaskill in Missouri and Republican Attorney General Mike DeWine defeating Democrat Richard Cordray in the race for Ohio governor.

The White House for days has stressed the historical headwinds it faced: In the last three decades, 2002 was the only midterm election when the party holding the White House gained Senate seats. And only twice in the past eight decades has the president's party picked up House seats in the midterms.

Trump's scorched-earth campaigning came to define the 2018 campaign. In the final days, he sought to motivate supporters with the battle over the confirmation of Supreme Court Justice Brett Kavanaugh. He said today that voters rebuked Senate Democrats over how they treated Kavanaugh during his confirmation hearings.

Returning to his immigration-heavy 2016 playbook, Trump went on to unleash his full fury on a caravan of migrants slowly making their way to the southern border.

His approach troubled many Republicans seeking to appeal to moderate voters in suburban House districts, but Trump prioritized base voters in the deep-red states that could determine the fate of the Senate.