WASHINGTON – While President Donald Trump publicly touted Republican midterm wins in the Senate, the White House began bracing Wednesday for a Democratic-controlled House that could tie up his agenda and unleash a series of investigationsinto his administration, decisions and personal finances.

Though Democrats did not catch the “blue wave” some predicted, the party picked up dozens of competitive House contests and claimed control of a chamber that will serve as a check on the president – while also giving him several high-profile adversaries to campaign against.

Trump, who remained mostly out of sight Tuesday after a whirlwind tour ahead of the election, was eager to focus on Republican successes in the Senate, where battleground wins in Indiana, Tennessee and Missouri appeared to validate the president’s schedule of campaign rallies in those states.

“Tremendous success tonight,” Trump posted on Twitter late Tuesday. “Thank you to all!”

But as Trump hunkered down to watch returns at the White House with family and friends, he saw Democrats pick up seat after seat in the House, many in swing suburban districts that will likely be crucial to his own reelection effort in 2020.

With each flipped seat, his plans to reduce taxes further and pursue stricter immigration controls faded.

More:Elections 2018 US House race results

“There will be gridlock,” predicted Michael Caputo, a former Trump campaign aide. "There will be more than two dozen investigations conducted by at least four House committees.”

Democratic control of the House also kept open the prospect of an impeachment, a move Democratic leaders have downplayed but that some on the left have declined to rule out. Many Republicans believe impeachment proceedings would represent an overreach and would help the GOP in 2020.

Rep. Nancy Pelosi, D-Calif., who is expected to reclaim the speaker's gavel in the House, struck a bipartisan tone in remarks late Tuesday.

"Tomorrow will be a new day in America," Pelosi told supporters in Washington.

The White House said Trump called Pelosi along with other congressional leaders and candidates.

More:U.S. House: Democrats move closer to control of Congress

More:Republicans make history by keeping Senate while losing House

Although the White House has raised the idea of working with Democrats – particularly on infrastructure – Trump's legislative agenda will likely be mostly thwarted by the shift. Analysts said the partisan divisions that have plagued Washington will be difficult to overcome now.

During the campaign, Democratic leaders signaled they would investigate Trump's relationship with Russia during the 2016 election, subpoena the tax returns he has refused to disclose and probe any number of administration actions, from alleged conflicts of interest to claims of profiteering in office.

House Democrats would press for more information about the interactions between Trump's real estate empire and his decisions in office, including whether members of the president's Mar-a-Lago resort in Florida are influencing executive decisions. They are also sure to seek additional documents related to Cabinet controversies, including the multiple probes of Interior Secretary Ryan Zinke.

There is pent-up desire among many Democratic lawmakers to confront Trump. Control of the House gives them new subpoena power, along with the ability to kill his legislative proposals.

"Gridlock and investigations," predicted Republican strategist Liz Mair.

Administration officials, speaking on the condition of anonymity, said they have been considering strategies to deal with a Democratic majority, including the possibility of pushing back hard on expected investigations by targeting lawmakers including Reps. Jerrold Nadler, D-N.Y., and Adam Schiff, D-Calif., who are likely to be leading them.

Nadler and Schiff, vocal Trump critics, would be in line to chair the House Judiciary and Intelligence committees, respectively.

Aides say the White House is also considering other strategies.

Trump can leverage Republican control of the Senate to continue to remake the federal bench by assigning judges who are likely to win confirmation. Like President Barack Obama, Trump could also rely more heavily on the use of executive orders to pursue policies on immigration and other contentious issues.

“Will he try to make deals with Democrats on things like infrastructure or even immigration or guns, given that Trump’s base might allow Trump to cut deals they wouldn’t for any other GOP president?” asked Doug Heye, a longtime GOP consultant. “Or, do we see an ever-escalating rhetoric and political tactics that only drive the country further apart?”

Several Republicans said Trump could gain some political advantage from having a powerful adversary in Democratic House leaders.

“Presidents sure love running against Congress and being able to distance themselves from unpopular lawmakers,” said Matt Schlapp, the chairman of the American Conservative Union. “The best guarantee for [Trump] getting re-elected is an impeachment effort in the House.”

Bruce Haynes, a former Republican campaign strategist, said a Democratic majority would not paralyze Trump. After all, the president has already had to deal with a slim GOP majority in the Senate that made it difficult to reach the 60-vote threshold required for most controversial legislation.

“It means he has the one thing that gives him energy and power: An opponent,” Haynes said.

White House press secretary Sarah Sanders predicted that "the president's agenda isn't going to change.” Instead, she encouraged Democratic leaders towork with the White House on tax cuts, immigration, the opioid epidemic and infrastructure.

In the weeks leading up to the election, Trump returned to immigration as a major theme, using the caravan of thousands of Central Americans winding its way through Mexico to renew calls for a border wall. Democrats have widely rejected the wall, and have said Trump was using the caravan to drum up support from GOP voters.

If the president hopes to secure federal funding for the barrier, he will likely have to pursue it during the coming lame duck session of Congress, before Democrats take control of the House in January.

As he campaigned in recent weeks, Trump increasingly downplayed Republican chances of keeping control in the House. Much of his frenetic schedule focused not on the House but instead on vulnerable Democratic Senate incumbents in states the president carried in 2016.

White House adviser Kellyanne Conway said the administration will deal with House investigations as they come up. In the meantime, she said, Trump will seek to work with Congress on issues like immigration and infrastructure.

Voters don’t want resistance or obstruction, she said.

Asked what would happen if, for example, the House Democrats sought Trump’s tax returns, Conway said the administration would talk to its lawyers.

She then echoed a favorite line of the president’s when the future isuncertain: “We’ll see what happens.”