WASHINGTON – If Democrats have been a thorn in President Donald Trump’s side while in the minority, just wait.

Some of his sharpest critics are among those in line to lead committees if Democrats win majority control of the House. They would have the power to issue subpoenas, call hearings and generally make Trump’s life miserable.

Imagine the 3 a.m. tweets from Trump if Democrats use that power to probe whether he has financial ties to Russia and financial conflicts of interest or to subpoena the tax returns he’s been reluctant to disclose. All of that would come on top of special counsel Robert Mueller’s ongoing investigation into whether the Trump campaign colluded with Russia to influence the 2016 presidential campaign.

Democrats have campaigned on lowering the cost of health care and prescription drugs, infrastructure improvements and cleaning up corruption in Washington. Their oversight agenda isn’t set, but those campaign promises are likely to inform it.

“Our challenge will be to overcome the Trump administration’s stonewalling and to keep the focus on the answers that the American people are owed from their government,” said Ashley Etienne, spokeswoman for House Minority Leader Nancy Pelosi.

Republicans are worried. House Speaker Paul Ryan’s political operation sent out a flyer, obtained by USA TODAY, to donors and industry leaders listing the Democrats they believed would be in leadership and the top committee slots.

"Don’t let this happen, support Team Ryan today!" the flyer read.

Still, Democrats shouldn’t start an oversight effort saying, "Now we’re going after President Trump," said former Rep. Henry Waxman, a California Democrat who chaired the House Committee on Oversight and Government Reform from 2007 to 2009. That would be "politicized" and "not credible."

But they could look into, for example, whether the Trump administration has turned its back on protecting people’s health or the environment or trying to make the tax code fair, he said.

“I think that there are many legitimate oversight issues, and I think if those issues are reviewed in an honest and fair way, this administration’s going to be embarrassed, because they haven’t done the job they should have been doing,” he said.

Here are some House members who would be poised to lead oversight efforts.

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Nancy Pelosi of California

If Pelosi regains her former title of House speaker, she’ll play a leading role in shaping the narrative and scope of oversight efforts.

Centrist Democrats will likely want to pursue a cautious approach, while some progressives will want aggressive oversight of the administration.

“Make no mistake – whoever next becomes speaker, whether they are a Democrat or a Republican – needs to provide complete oversight of this reckless, criminal administration starting on day one,” Tom Steyer, the billionaire activist who has called for Trump’s impeachment, said in a statement to USA TODAY.

During a recent forum at the Harvard Kennedy School’s Institute of Politics, Pelosi said the calls for Trump's impeachment were "very divisive." But she said Democrats would make sure the Mueller investigation’s documentation is preserved for further examination of Russian interference in the 2016 election.

Pelosi blasted Republicans during the forum for providing "absolutely no oversight" of government agencies. She has already convened meetings with members in line to chair committees to talk with them about their approach and coordination.

"This shouldn’t be scattershot," she said. "This should be responsible, honoring our Constitution and our responsibilities, seeking the truth and, in terms of the agencies of government, having the proper oversight to make sure that we are exercising our balance of power."

Elijah Cummings of Maryland

While Cummings was often critical of Trump over the course of the 2016 election – the congressman at one point called Trump "dangerous" – the two still met for an hour in the Oval Office in March 2017 to discuss a proposal to lower prescription drug prices.

"Great discussion," Trump tweeted after the meeting. (He later said that Cummings proclaimed he'd be one of the country's "great presidents," something Cummings denied.)

Cummings said he got "radio silence" from Trump after that meeting, thus ending that brief brush with bipartisanship.

If Cummings chairs the House Oversight and Government Reform Committee, he would have jurisdiction over a broad array of topics. The rising costs of drug prices, along with other everyday issues confronting Americans, would be one part of his mission. Another would focus on waste, fraud and abuse in the Trump administration, according to a Democratic aide.

That could include oversight on topics such Trump’s potential financial conflicts of interest and protecting against violations of the Constitution’s “emoluments clause," which prohibits officeholders from accepting payments from foreign governments without consent from Congress. Potential violation examples could include foreign government officials who buy up floors of Trump's hotel rooms or pay higher-than-market rents at Trump Tower, according to committee Democrats.

Other topics could include the handling of security clearances, attacks on government watchdogs and employees, ethics scandals involving senior administration officials and Trump’s immigration and child separation policies at the southern border.

Adam Schiff of California

When House Republicans in March concluded there was no collusion between the Trump campaign and Russia, Schiff called the end of that yearlong probe a “terrible disservice to the country and the American people.”

A former federal prosecutor, he said as early as February that there was "ample evidence" that the Trump campaign colluded with Russia in 2016, though he left it up to Mueller to prove beyond a reasonable doubt.

Schiff is likely to chair the House Intelligence Committee if Democrats win the House, and he’s not ready to give up on the investigation.

He said in a statement that Democrats would need to "fully assess what areas of inquiry in the Russia investigation still require a full accounting" by reviewing their work along with what the Senate and Mueller have uncovered.

“There are serious and credible allegations the Russians may possess financial leverage over the president, including perhaps the laundering of Russian money through his businesses,” Schiff said in an Oct. 12 op-ed in the Washington Post. “It would be negligent to our national security not to find out.”

Jerrold Nadler of New York

Nadler could chair the House Judiciary Committee, which has jurisdiction over articles of impeachment.

So far, he has been guarded about his position, telling The Atlantic in September that he hasn’t seen information that’s “proof positive that he’s committed impeachable offenses.”

Regardless, it’s clear Nadler would pursue a vigorous oversight agenda. A report by the committee’s Democratic staff called “A Record of Abuse, Corruption, and Inaction,” blasts the GOP majority for failing to conduct meaningful oversight on a host of issues, including election security, enforcement of federal ethics rules, breaches of the emoluments clause of the Constitution and allegations of obstruction of justice.

He told The New York Times last month that, if Democrats win control, the committee would open an investigation related to allegations of sexual misconduct and perjury against Justice Brett Kavanaugh, arguing the Senate failed to do its job of “advise and consent.” He said the committee would likely subpoena records from the White House and FBI, which conducted an investigation into the allegations that Democrats said wasn't thorough enough.

Nadler has also been a critic of Trump’s immigration policies, another topic that falls under the committee’s jurisdiction.

“The abuses and ethical lapses we have seen in the Trump Administration, in the Trump Campaign and in Congress clearly show the need to address the culture of corruption that has developed in the absence of appropriate checks on power,” Nadler said, delivering the weekly Democratic Address last month. “This corruption is at the heart of what Donald Trump represents: self-interest and ego-driven decisions that come at the expense of the American people.”

Maxine Waters of California

Waters was among more than a dozen Democrats and high-profile critics of Trump who were targeted last month with suspicious packages carrying bomb-like devices. She blamed Trump for promoting violence among his supporters and urged others to not be intimidated.

"We have to keep to doing what we’re doing in order to make this country right,” she said in an interview with Blavity. “That’s what I intend to do, and as the young people say, 'I ain’t scared.’”

If Democrats win the House, Waters would be in line to lead the House Financial Services Committee. That means more power to explore a key interest – Trump’s finances.

She has been seeking records that could show whether Trump, his family members and associates have financial ties to Russia.

She would also be in position to review Republican efforts to roll back Dodd-Frank Wall Street reform protections.

"Financial services issues are critical for all Americans and for our economy, and I am focused on making sure that our financial system is fair,” she said in a statement.

Waters, who has long called for Trump’s impeachment, made waves this summer when she encouraged protesters to confront Cabinet officials in public. Trump responded by calling her “an extraordinarily low-IQ person” and alleging falsely that she called for harming his supporters.

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Contributing: Eliza Collins