For now, Democrats can only ask for the “tapes” that President Donald Trump has suggested may exist of his conversations with fired FBI Director James Comey. But if the party takes back the House next year, it can subpoena them.

The supposed "tapes" are just one of a number of issues Democrats are already plotting to pursue if they win control of Congress’ vast arsenal of investigative powers — raising the stakes on the 2018 congressional midterm elections.

"When we take back the House in 2018, Democrats are going to hold this administration accountable,” said Rep. David Cicilline, D-R.I., a member of the party leadership. “And we'll make sure there are real consequences for anyone who tries to use their elected office for personal gain...especially President Trump.”

If Democrats win the 24 seats they need to retake the House, they wouldn't just get the ability to block Republicans' legislative agenda, along with the president's. They would also gain control of Congress’ oversight authority, which they could use to dig into everything from Trump's possible ties to Russia to his alleged business conflicts of interests to potentially even his tax returns.

They could flood the Trump administration with subpoenas, compel testimony from witnesses, schedule public hearings, issue reports, and create special committees like the one Republicans started to probe Benghazi.

The Oversight Committee, for instance, has the largest House staff outside the Speaker's Office, with over 120 attorneys, investigators and support staff, according to a former committee aide.

“They have the power to go after every executive agency — and it’s basically unlimited,” said former Rep. Tom Davis, R-Va., who was the top Republican on the Oversight Committee when Democrats wielded that power against George W. Bush during his final two years in the White House.

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Davis said that while Trump has plenty of time to change the trajectory of his administration, history has proven that a determined opposition party can tangle up a White House's agenda with control of even just one chamber of Congress. “Anything the president wishes to accomplish at that point is almost nixed,” he said.

Trump presents a uniquely target-rich environment, Democrats say.

“By the time we get to January of 2019, I expect there’d be just treasure troves of things to investigate,” said Rep. John Sarbanes, D-Md., a member of the Oversight Committee who also chairs his party’s Democracy Reform Task Force, which was established to catalog Trump ethical issues until the party has the power to act on them.

“We’ll definitely be ready if we can get the gavel,” Sarbanes said.

Of course for now, this is all just Democratic revenge fantasy, since the election is more than a year and half away. They have little hope of retaking the Senate in 2018 and winning the House will be a major challenge.

But Democratic leaders said that leading up to the election, they’ll make sure voters hear that Republicans in Congress have given Trump a pass in their responsibility to put a check on the executive branch.

“The Republicans need to stand up and smell the cover-up,” Democratic National Committee Chairman Tom Perez, a former federal prosecutor, said during a conference call with DNC officials Friday. “I’ve prosecuted a lot of a obstruction of justice cases, and this has that feel."

Some of Democrats' criticism falls on current Oversight Committee Chairman, Rep. Jason Chaffetz, R-Utah, who recently announced his retirement.

Chaffetz said before the election that he had two years worth of investigations already lined up on Hillary Clinton. But after Trump won, Chaffetz has taken a notably lighter touch, declining to investigate former National Security Adviser Michael Flynn, among other possible matters.

Rodell Mollineau, the former president of the Democratic opposition research group American Bridge, said Democrats know first-hand from Republicans’ probes of the Obama and Clinton White Houses how distracting the investigations can be.

“The amount of paperwork and prep that his administration would have to deal with getting ready for a hostile hearing would bring the White House to a standstill. Also, the more questions they are forced to answer, the more likely someone will perjure themselves,” he said.

U.S. Rep. Elijah Cummings (D-MD). Alex Wong / Getty Images

If Democrats win, the Oversight gavel would likely go to Rep. Elijah Cummings, D-Md., the committee’s ranking member.

Kurt Bardella, a public relations expert who worked for Rep. Darrell Issa when the California Republican chaired the panel and often sparred with Cummings, said the shift in power that comes with transitioning from the minority to the majority can be heady.

“It can be an incredibly crippling function if exercised in a way that it almost certainly would be if Democrats took (the Oversight Committee) back,” Bardella said. “It would be exercised in probably the most robust way in the committee’s history.”