House Democrats plan to review Trump's role in hush money payments in next Congress, source says The Democrats will take control of the House in January and gain subpoena power.

The House Oversight Committee plans to investigate Donald Trump's involvement in hush payments made to women during the 2016 presidential campaign, a senior Democratic aide on the committee told ABC News.

When the Democrats take control of the House in January and gain subpoena power, they plan to probe the president's role in payments to two women who alleged during the 2016 campaign that they had affairs with Trump, according to the aide.

Democratic members on the committee have already begun digging into the president's involvement, according to the aide. In September, the committee requested documents from the Trump organization, the aide added.

Trump has long denied that he knew of the payments, and has denied having affairs with the women.

The story was first reported by the Wall Street Journal.

The White House did not immediately respond to ABC News' requests for comment.

In a statement to ABC News, Trump's lawyer Rudy Giuliani called the effort "useless."

"Since the payments were not campaign contributions based on the FEC rulings it would be as useless as Mueller’s absurd investigation of Russian collusion, which has established that the only Russian involvement was collusion with Hillary and DNC to produce fraudulent Steele dossier," Giuliani said in the statement. "You insist on calling it a hush payment, which is an opinion not a fact. Payments for confidentiality in settling claims is common and the amounts involved here, not millions but $150,000 and $130,000, means the case was considered as harassment not as a serious claim. Look at the serious settlements with billionaires and companies and few are at this level and they are the nuisance suits."

Adult film actress Stormy Daniels, whose real name is Stephanie Clifford, received a payment of $130,000 from Trump's former personal attorney Michael Cohen during the presidential campaign to keep quiet about an alleged sexual encounter she had with Trump in 2006.

Trump has denied the allegation and maintained that he did not know about the settlement agreement until after it was signed.

Trump only publicly acknowledged awareness of the payments after Giuliani said in April on Fox News that Trump paid Cohen back for the costs associated with the Stormy Daniels deal. Giuliani contended that the payments were for purely personal reasons and that no campaign finance laws were broken.

Karen McDougal, a former Playboy centerfold model, signed a $150,000 pact with American Media Inc., the publisher of the National Enquirer, in August 2016. The company purchased the rights to her story -- in which she claimed to have had a 10-month romantic affair with Trump in 2006.

Trump denied that romantic relationship, too. "This is an old story that is just more fake news," a White House spokesperson previously told ABC News.

In August, Cohen pleaded guilty in federal court to eight counts related to illegal campaign contributions "in coordination and at the direction of a candidate for federal office," -- a reference to Trump. The campaign finance violations were associated with Cohen's role in alleged hush money agreements.

Cohen, who used to describe himself as the "guy who would take a bullet" for the president, has since met with investigators from the office of the special counsel, Robert Mueller, which is looking into Russia's meddling in the 2016 election and alleged collusion with Trump's campaign.

This is not the first effort by the Democrats to investigate Trump. Several Democratic members of the House Ways and Means Committee stated last week that they planned to review Trump's tax filings, to which Trump responded, "I don't care. They can do whatever they want and I can do whatever I want."

On "This Week" Sunday, incoming Oversight Committee chair Rep. Elijah Cummings told ABC News Chief Anchor George Stephanopoulos that the committee will investigate the president, but will do so judiciously.

“I'm not going to be handing out subpoenas like somebody's handing out candy on Halloween. I take this as a lawyer and as an officer of the court. I take subpoenas very seriously and I plan to, if I have to use them, they will be used in a very, in a methodical way, and it must be in the public interest,” Cummings said.

ABC News' Wil Cruz contributed to this report.