When Democrats officially take control of the U.S. House of Representatives on Thursday, a group of President Trump's top critics will have new powers. For the past two years, Democrats have been in the wilderness when it comes to leverage in Congress and have been eager to conduct oversight of the president.

Until now, the highest ranking Democratic lawmakers on key committees have had limited reach, essentially relegated to voicing their concerns through cable news programs and social media. Now, the change in power, issuing from November's midterm elections, not only gives them a megaphone but also real legislative tools, like the power to issue subpoenas, to hold the president to account on everything from his tax returns and business dealings to the Russia investigation to administration scandals and his immigration policies.

Here are five members to watch in the New Congress and what they hope to achieve:

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New York Rep. Jerry Nadler, chair of the House Judiciary Committee

President Trump and the Manhattan lawmaker have a history that predates his presidency. The two battled over New York City real estate projects when Mr. Trump was a developer and Nadler a state assemblyman and then later, a congressman. This led to Mr. Trump dubbing Nadler "one of the most egregious hacks in contemporary politics."

The relationship will now become even more consequential, since any moves to impeach Mr. Trump would likely begin in Nadler's committee. But Nadler, who was a fierce defender of President Clinton against impeachment, has been exercising caution about proceeding in the era of Trump. "There's certainly a lot of allegations, but we'll have to wait and see what the Mueller investigation comes up with and other investigations looking into it," Nadler told "CBS This Morning" on Wednesday.

Instead, Nadler says he's prioritizing oversight. His committee has already called upon acting Attorney General Matthew Whitaker because Democrats are concerned about the nature of his appointment and its relation to the Russia investigation. Nadler said that Whitaker has agreed to testify, but hasn't committed to a date. He says he'll issue a subpoena if necessary. The incoming committee chairman is also determined to protect the special counsel investigation led by Robert Mueller.

"For the last two years, the president has had no oversight, no accountability from Congress. The Republican Congress was completely derelict in its responsibility to provide oversight," Nadler told "CBS This Morning." "We're going to provide that oversight. We're going to use the subpoena power if we have to."

California Rep. Adam Schiff, chair of the House Intelligence Committee

FILE: Rep. Adam Schiff, D- Calif., ranking member of the House Intelligence Committee, speaks at the University of Pennsylvania in Philadelphia, Thursday, Feb. 1, 2018. Matt Rourke / AP

Once a model in bipartisanship, the House Intelligence Committee suffered a high profile partisan breakdown in the Trump administration around the investigation into Russian meddling in U.S. elections. Republican Chair Devin Nunes and Ranking Member Adam Schiff and their counterparts in the committee sparred over intelligence gathering and findings, releasing competing memos and holding competing press conferences.

When he takes the reins of the committee, Schiff has said he will focus the panel's efforts around protecting the Mueller investigation and re-engaging it in the overall probe. Schiff has also expressed interest in calling back witnesses related to the Russia investigation who have already testified. "We believe other witnesses were untruthful before our committee," Schiff said in November, after Trump's former attorney Michael Cohen pleaded guilty to lying to Congress.

Schiff has identified two key areas of interest when it comes to the Russian investigation and possible collusion between Trump associates: The details of the infamous Trump Tower 2016 meeting, which could involve issuing subpoenas for phone records, and whether Russians laundered money through the Trump organization.

"What would be most compromising to our nation and our national security is if a hostile foreign power has leverage over the president of the United States," Schiff told the New York Times.

While the bulk of the focus will likely be on Russia, Schiff has also said he would like more scrutiny of the murder of journalist Jamal Khashoggi and the related intelligence conclusions, as well as a broader examination of the U.S. relationship with Saudi Arabia.

Maryland Rep. Elijah Cummings, chair of the House Oversight and Reform Committee

Congressman Elijah Cummings speaks after meeting with President Donald Trump at the White House on March 8, 2017 in Washington, DC. Sipa USA via AP

If Democrats have been craving oversight of the president, they will certainly be watching Cummings, as the chair of the committee with oversight in its name. Cummings has said he would use his power to make Mueller's findings public. "What the public has said is they want accountability and transparency," Cummings told CBS' "Face the Nation." "I would do anything and everything in my power to have the findings presented not only to the Congress but to the people of the United States." Cummings has also said he would like Cohen to come before the committee. "The public needs to know exactly what happened," he told CNN's "State of the Union." "There's a lot to look at."

But Cummings has also been cautious about overreach, and says he wants to keep the committee's focus on issues having a direct impact on Americans. On the "Face the Nation," Cummings identified four main areas of interest: protecting and expanding voting rights, fairness in the U.S Census, the economic troubles of the U.S. Postal Service, and addressing the rising cost of prescription drugs.

"I plan to run our committee like a federal court room...I want civility and we will address subpoenas in a very systematic way," Cummings told CNN. "The American people want government to help them not hurt them...I'm not looking for headlines, I'm looking to get things done for them."

California Rep. Maxine Waters, chair of the House Financial Services Committee

Honoree Congresswoman Maxine Waters attends the Black Girls Rock! Awards at the New Jersey Performing Arts Center on Saturday, Aug. 5, 2017, in Newark, N.J. (Photo by Charles Sykes/Invision/AP) Charles Sykes

Waters has become a hero of the the anti-Trump resistance--and a top target of the president's attacks. Now, she will become the first woman and first African-American chair of the Financial Services Committee, and she has her eye on the banks that lent Mr. Trump money.

As ranking member of the committee, Waters has been focused on Deutsche Bank, which lended Trump money after bankruptcies, and was also hit with a large fine for a $10 billion Russian money laundering scheme.

In 2017, Waters and committee Democrats sent a letter to Deutsche Bank's CEO seeking information about its internal reviews. Deutsche Bank's chief executive officer requesting information on two internal reviews. "Deutsche Bank's pattern of involvement in money laundering schemes with primarily Russian participation, its unconventional relationship with the President, and its repeated violations of U.S. banking laws, all raise serious questions about whether the Bank's reported reviews of the trading scheme and Trump's financial ties to Russia were completely thorough," the lawmakers wrote at the time. Waters also wrote to demand then-Attorney General Jeff Sessions recuse himself from any investigation by the Justice Department of Deutsche Bank.

And as ranking member, Waters asked Treasury Secretary Steven Mnuchin to detail any financial ties Trump or his family members may have to Russia.

Beyond those inquiries, Waters has said she wants to focus on protections for consumers, expanding affordable housing, encouraging innovation in financial technology, expanding diversity in the financial services industry, according to a statement.

Massachusetts Rep. Richard Neal, chair of the House Ways and Means Committee

https://neal.house.gov/

Unlike recent predecessors, the president has refused to release his tax returns. That could change once Neal takes the helm of the tax-writing Ways and Means Committee. "Yes, I think we will," Neal told the Associated Press whether he would request the president's taxes. "I hope that the president would do this on his own, largely because every president since Gerald R. Ford has voluntarily done this."

Mr. Trump has repeatedly declined to make his returns public, protesting that he is under audit. If he doesn't comply with Neal's request, the tax code provision allows the chairman to request the taxpayer's information from the Internal Revenue Service and the treasury secretary would have to produce it. "We will work with our general counsel and the I.R.S. general counsel on any requests," Mnuchin told the New York Times last year, shortly before Democrats won control of the House.

Beyond taxes, Neal will play a prominent role when it comes to top items of the president's agenda--from tax reform changes to Obamacare to new trade deals. "We intend to enshrine the principle of preexisting condition as a guarantee of our national network through the Affordable Care Act," Neal said in a press conference after the midterm elections.