Donald Trump’s presidential transition team on Saturday challenged the veracity of U.S. intelligence assessments that Russia was trying to tip the November election to the Republican. A top Senate Democrat demanded a full congressional investigation.

The CIA has now concluded with “high confidence” that Moscow was not only interfering with the election, but that its actions were intended to help Trump, according to a senior U.S. official. The assessment is based in part on evidence that Russian actors had hacked Republicans as well as Democrats but were only releasing information harmful to Trump’s rival, Hillary Clinton.

The official was not authorized to discuss the private intelligence assessment publicly and insisted on anonymity.

Trump’s public dismissal of the CIA assessment raises questions about how he will treat information from intelligence agencies as president. His view also puts Republicans in the uncomfortable position of choosing between the incoming president and the intelligence community.

In a statement late Friday, Trump’s transition team said the finger-pointing at Russia was coming from “the same people that said Saddam Hussein had weapons of mass destruction.” On Saturday, spokesman Sean Spicer told CNN there were “people within these agencies who are upset with the outcome of the election.”

Spicer denied a New York Times report that Russia had broken into the Republican National Committee’s computer networks. The U.S. official who disclosed the CIA assessment to The Associated Press said only that Republican entities had been targeted during the election.

Democratic Sen. Chuck Schumer, D-N.Y., said he would press for a congressional investigation in the new year. “That any country could be meddling in our elections should shake both political parties to their core,” he said. “It’s imperative that our intelligence community turns over any relevant information so that Congress can conduct a full investigation.”

Republican Sens. John McCain of Arizona and Lindsey Graham of South Carolina have also said they plan to pursue investigations into Russian election interference. Other Republicans have played down the reports. Texas Sen. John Cornyn wrote on Twitter Saturday that Russian hacking had been going on for years. He said the matter was “serious, but hardly news.”

There was no immediate official response from Moscow. But Oleg Morozov, a member of the foreign relations committee in the upper house of the Russian parliament, dismissed the claim of Russian interference as “silliness and paranoia,” according to the RIA Novosti news agency. Morozov described the allegations as an attempt to force the next administration to stick to Obama’s anti-Russian course.

President Barack Obama has ordered a full-scale review of campaign-season cyberattacks to be completed before he leaves office in January.