Following DHS Reveal of the 21 States Hacked by Russia Clapper Calls Trump's Election Win Into Doubt

James Clapper, the former director of national intelligence, said the US intelligence community's assessment of Russia's interference in the 2016 election "cast doubt on the legitimacy" of President Donald Trump's victory.

"Our intelligence community assessment did serve to cast doubt on the legitimacy of his victory in the election," Clapper said of Trump in a CNN interview Friday evening.

"I think that, above all else, is what concerned him, and I think that transcends, unfortunately, the real concern here, which is Russian interference in our political process which, by the way, is going to continue," Clapper said.

It was the most direct assertion about the impact that Russian operatives had in the US election — the investigation of which has evolved exponentially in the last four months under special counsel Robert Mueller, who is overseeing the Russia probe on behalf of the US Justice Department.

Mueller and his investigators have focused on several people close to Trump who have ties to, or have made contact with the Kremlin — including former campaign chairman Paul Manafort, former national security adviser Michael Flynn, and others. Information gleaned from US government surveillance of Manafort prompted concerns that he had encouraged Russians to "help with the campaign," according to a CNN report on Monday.

Kremlin operatives reportedly bragged about trying to use people close to Trump — like Flynn, Manafort, and former foreign-policy adviser Carter Page — to make inroads with the campaign.

And Donald Trump, Jr. became the subject of heavy scrutiny in July when it was discovered that he, along with Manafort and the president's son-in-law, Jared Kushner attended a meeting with a Kremlin-linked Russian lawyer who promised to deliver dirt on Hillary Clinton.

Russia's efforts to sway the US election were further revealed this month when Facebook announced that Russian-associated Facebook accounts had purchased $100,000 in ads during the election. The ads were used to target voters in some battleground states.

Clapper's assertion that Russia's activities cast doubt on Trump's legitimacy strikes a nerve with the president. Aides and allies have said previously that Trump's ire toward the Russia investigation stems from that exact notion; that Russia's meddling potentially diminishes his November 2016 victory.

Trump himself is a subject of Mueller's investigation for possible obstruction of justice, for his part in the firing of former FBI Director James Comey. Trump has said that he had the Russia probe in mind when he made his decision, and later said that firing Comey took "great pressure" off of him in the investigation.

To date, neither Trump nor anyone subject to Mueller's investigation has been accused of any wrongdoing, and Trump has denied the same.

The federal government told election officials in 21 states on Friday that hackers had tried to break into their systems before the 2016 election, the Associated Press reported.

Key battleground states like Florida, Wisconsin, Ohio, Pennsylvania, and Virginia were among those targeted, the report said. The AP said the government did not specify who the hackers were, but election officials in several affected states told the news wire service that the attempts were linked to Russia.