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Robert Mueller may be just one of President Donald Trump's worries if the Democrats seize control of the House of Representatives this fall. For a year-and-a-half, Democrats have been hounding Republicans to launch investigations into every Trump scandal-du-jour, pushing for more information on everything from Housing Secretary Ben Carson's $31,000 furniture purchase to Jared Kushner's alleged conflicts of interest. Lacking the subpoena power that comes with control of the chamber, Democrats have been forced to sit on the sidelines as the clamoring from their base has ratcheted to a fever pitch. But that will change if they manage to flip the 23 seats they need to secure the House in November, as they are narrowly favored to do. "All of these incidents that have been a blur for us in terms of the news cycle are going to turn into inquiries," said Michael Volkov, an expert in government investigations who has served as an attorney in the Justice Department and for the Senate and House judiciary committees. Volkov, who has represented individuals and businesses before Congress, said things were about to get "wild." Experts expect Democrats to pursue controversial items like Trump's tax returns, and to delve into his business dealings from decades ago. They may also seek public hearings with Trump family members, including Donald Trump Jr., who is a key figure in the Russia investigation. Democrats could also go after top officials like Commerce Secretary Wilbur Ross, who has faced scrutiny over his financial dealings. "There is no question that there will be an exponential increase in requests from Congress going to the administration if Democrats take one of the chambers," said Justin Rood, who directs the Congressional Oversight initiative at the nonpartisan Project On Government Oversight. Susan Del Percio, a political strategist who analyzes the Republican Party, called it the White House's "worst nightmare." Trump's White House has already struggled with a number of high-profile controversies even with the relatively lax oversight they have faced from a Republican Congress. Key officials, including EPA Administrator Scott Pruitt, Health and Human Services Secretary Tom Price, and communications director Anthony Scaramucci have already left the administration under the cloud of scandal.

Democrats promise strong oversight

Democratic leadership has largely remained quiet on specific targets — and has played down the prospects for impeachment — although they have vowed to be aggressive. Maryland Rep. Steny Hoyer, the second-ranking Democrat in the House, told CNBC that the party "will not shy away from standing up to President Trump and conducting oversight." It's a prospect that House Speaker Paul Ryan has said could lead to "chaos." If the Democrats take control, their staff on the powerful oversight committee will double, and virtually all of the new positions will be filled by investigators, according to Kurt Bardella, a former spokesman for Rep. Darrell Issa, R-Calif., who was the top Republican on the oversight committee when the Republicans took control of the House in 2010. "I am certain that the Democrats on the committee are getting flooded with resumes," Bardella said. The first thing Democrats are likely to do is issue all the subpoenas the Republicans refused to issue while they were in the majority, Bardella said. That process could be extensive. Republicans on the oversight committee have blocked 52 subpoena motions, according to Democrats' latest tally. "The oversight committee uniquely has the ability to completely overrun any agenda or message that the administration is trying to focus on that day," Bardella said. "For a president who is more obsessed with public relations than any president in history, that will be untenable." Issa, who has been called Obama's toughest critic, led the Republican charge against the 44th president in the House, overseeing the investigations into the "Fast and Furious" controversy over alleged gun-running to Mexico and the administration's handling of the 2012 Benghazi attack. Rood, who previously served as a congressional investigator for Sen. Tom Coburn, R-Okla., said no one really knows what will get investigated. But, he added, one-sided oversight would not be sufficient to deal with the most important issues Congress is charged with scrutinizing. "When you're talking about doing some sort of serious examination of serious issues that affect our ability to govern ourselves fairly and freely, it needs to be done by both sides," he said.

White House 'prepared to handle whatever'

A former senior Trump administration official, who declined to be named, told CNBC that the White House is prepared for what may come — and hasn't given up on the fight for Congress. "One, I think the White House is bullish on winning the congressional election," the former official said. "Two, in the event that they don't win, in the event that Democrats take over Congress, oversight is something that the opposing party has used against administrations for years." The White House did not respond to a request for comment. The former official said that it was "telling" that the White House hired Emmet Flood in May. Flood, who was tapped to lead the White House's legal response to Mueller's Russia probe, is a veteran of the Washington legal establishment who has largely avoided the limelight since joining the Trump team. Flood advised Bill Clinton during his impeachment proceedings. His firm, Williams & Connolly, represented Hillary Clinton. "Flood has experience and respect in Washington, and handled very high-profile oversight matters and congressional inquiries," the former official said. The former official said Flood "is certainly prepared to handle whatever" Democrats throw his way. The former official suggested that executive privilege claims would be "front and center when dealing with oversight." Executive privilege could be a tricky defense against inquiries into matters that do not directly pertain to the White House, said Daniel Jacobson, a former lawyer in Obama's office of White House Counsel. "They can bring in the best lawyers they want, but at the end of the day they won't be able to stop Congress from doing its job," he said. Presidents have often claimed executive privilege — or the right to withhold information to protect the public interest — to keep information from Congress, though the claim can be challenged in court. In 2016, U.S. District Court Judge Amy Berman Jackson denied Obama's claim of executive privilege during the "Fast and Furious" controversy. Jacobson noted that the extent of the damage that Democrats may be able to do has not been fully realized, because "the public only sees what it sees." "The current Congress shielding the administration from public hearings has had a huge impact that you just haven't seen," he said.

The current Congress shielding the administration from public hearings has had a huge impact that you just haven't seen. Daniel Jacobson former Obama administration lawyer

For instance, he said, had the Democrats been in control of the House in June when Trump's zero-tolerance immigration policy was dominating political coverage with stories of children being separated from their parents, a public hearing with Attorney General Jeff Sessions might have been devastating. It's not clear what the White House strategy will be to respond to the public relations issues raised by the investigations, but Republican strategists are taking their cues from how the president has responded in the past. The White House "will do what they always do, which is to double down and attack," said Ryan Williams, a Republican strategist and a former longtime spokesman for Mitt Romney. "The president likes a foil." Williams said it was possible that the Democrats could overplay their hand, particularly if they draw up articles of impeachment. But, he said, much still depended on the outcome of Mueller's investigation, and whether the special counsel provides new, potentially damaging details to the public.

Slowing down the bureaucracy