After two years of a compliant Congress, Trump can expect scrutiny into alleged collusion, obstruction and corruption

When Democrats formally assume the US House majority in January for the first time in eight years, they will contend with a president long dubbed by most members of their party as unfit and unqualified to serve.

But for the first time in the two years since Donald Trump’s inauguration, Democrats will no longer be watching or protesting from the sidelines.

Fresh off a major victory in the November 2018 midterm elections – which saw the party gain 40 seats in the House – Democrats are preparing to fully utilize the investigative authorities afforded to Congress as legal troubles continue to mount for the president and his inner circle.

And unlike their Republican counterparts, who were reticent to levy the powers of congressional oversight against Trump, nothing appears to be off limits.

The question before Democrats appears to be what not to investigate – and whether there’s any room for negotiation with a president who is anathema to the party’s base.

Nancy Pelosi, the House Democratic leader who is poised to retake the speaker’s gavel in January, declared on the night of the 7 November midterm elections that it was the responsibility of lawmakers in Washington to find common ground.

“We will strive for bipartisanship, with fairness on all sides,” Pelosi said in a victory speech after the House was called for Democrats.

“A Democratic Congress will work for solutions that bring us together, because we have all had enough of division. The American people want peace. They want results.”

But Pelosi, who in 2007 became the first woman to serve as House speaker, also issued a sharp warning to the White House, stating the election was “about restoring the constitution’s checks and balances to the Trump administration”.

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Trump has largely avoided scrutiny under a Republican-controlled Congress, despite a litany of issues that have alarmed government and ethics watchdogs since he took office.

Among the avenues Democrats plan to pursue are potential collusion between the Trump campaign and Russia in the 2016 election and possible obstruction of justice; Trump’s refusal to release his tax returns; hush money paid by the president’s former personal attorney Michael Cohen to women who alleged they had affairs with Trump; and the misuse of taxpayer dollars by members of the Trump cabinet.

There are also the president’s business dealings and efforts by foreign countries to influence his administration, as well as the increasingly blurred lines between Trump’s family business and the public office he now holds.

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“The American people have a right to know that their president is working on their behalf, not his family’s financial interests,” Adam Schiff, the incoming chairman of the House intelligence committee, stated in a recent interview. “Right now, I don’t think any of us can have the confidence that that’s the case.”

Schiff, a Democrat from California, publicly sparred with his Republican counterpart, Devin Nunes, who continued to hold close ties to the White House while overseeing the House intelligence committee’s own investigation into Russian interference in the 2016 election.

Other incoming Democratic chairmen have similarly vowed to fulfill the oversight responsibilities of Congress.

Elijah Cummings, a congressman from Maryland who is expected to take over the House oversight committee, issued 64 subpoenas over the last two years. But because he was in the minority, they went nowhere absent Republican support.

Now, he will have considerably more power and has said his mandate is to simply follow “what the constitution says I’m supposed to do”.

Arguably the most grave responsibility could fall on the New York representative Jerrold Nadler, the incoming House judiciary committee chairman. If special counsel Robert Mueller recommends charges against Trump in the Russia investigation, any potential impeachment hearings would occur on Nadler’s watch.

Facebook Twitter Pinterest Adam Schiff, left, is likely to take a radically different approach to oversight from the outgoing House intelligence committee chair, Devin Nunes, right. Photograph: Mark Wilson/Getty Images

Earlier this month, Nadler said court filings stating that Trump directed Cohen to pay hush money – a violation of campaign finance law that amounts to a federal crime – “would be impeachable offenses”.

Nadler said the alleged crimes, if true, “were committed in the service of fraudulently obtaining the office”.

Bracing himself for the onslaught of investigative peril, Trump has threatened to respond to Democrats with “a warlike posture”.

The already contentious climate has cast major doubts over whether there is any prospect of dealmaking.

Although Trump has touted a massive infrastructure bill and an immigration compromise, he has so far demonstrated antipathy toward the legislative process.

Donna Edwards, a former congresswoman from Maryland, said the most realistic strategy for Democrats would be to try to strike common ground with the Republican-led Senate and send legislation directly to the president’s desk.

“I don’t think they have a choice but to try to work with the president,” she said. “But there’s a limit, and the president goes into all of these negotiations [saying] ‘my way or the highway’.

“He clearly doesn’t understand what happens in legislation.”

Jim Manley, a longtime Democratic aide, said any semblance of cooperation “would require a radical shift in the president’s tone and tenor”.

“He made it clear that if Democrats conduct oversight, he’s going to refuse to work with them,” said Manley, who served as a top aide to the former Senate majority leader Harry Reid and the late Senator Ted Kennedy.

“No Democrat was cowed by that threat then, and no Democrat is going to be cowed by that threat now.”