In the tweets in question he refers dismissively to "the 'Intelligence' briefing," and suggesting that his upcoming briefing was delayed because "perhaps more time needed to build a case."
But all 16 U.S. intelligence agencies have concluded that the Russian government was behind the hacking.
McMullin wrote that after the tweet about Assange, Trump "has become a tool of foreign adversaries engaged in a direct assault on our democracy."
Little tweeted today, "Let's stare this reality square in the face: PEOTUS is pro-Putin and believes Julian Assange over the @CIA. On Jan. 20 we will be less safe."
"They've yet to be fully briefed by the intelligence community, yet they've issued a number of public statements that have sought to discredit the career professionals in the intelligence community," said Cohen, who now works as an ABC News consultant.
"They've been dismissive of allegations of Russian involvement, and they've mischaracterized information released by law enforcement and intelligence officials. In doing so, they have likely undermined their future relationship with those intelligence and law enforcement professionals."
Susan Hennessey, a fellow in national security law at the Brookings Institution, was quick to warn that it's inaccurate "to think of the intelligence community as a group that gets their feelings hurt very easily" but said the tweets could certainly have a lasting impact.
"Trump has essentially accused the intelligence community of being politicized, that they are producing this information for partisan reasons or to harm him ... That is a really, really significant accusation in the world of intelligence," she told ABC News.
"It does appear as though these tweets may be an attempt by Donald Trump to essentially discredit that report before it's issued," she said of the report ordered by President Obama on alleged Russian hacking. "That's really quite significant — essentially for your incoming boss to undercut the work you do before he takes office. That does have implications for the future of the relationship."
Steve Gomez, a former section chief in the FBI's directorate of intelligence, said Trump's briefing could include an abundance of specifics because of his apparent skepticism.
"If I sensed that the recipient of a briefing is maybe questioning or has some doubt over the conclusions that we reached in our intelligence product, then I would say to our staff who was producing [the information] that, 'Let's provide a greater level of detail in order to show how we've come to those conclusions,'" said Gomez, who is now an ABC News consultant.
"He's not from the government," he said of Trump. "He's not used to receiving classified sensitive briefings that are relying on intelligence from a myriad of sources."
The sources of that information — aside from the intelligence (which Trump sarcastically set in quotes) community — could become an issue as well, Cohen said.
"He seemingly has placed greater credibility in the statements of Julian Assange than the statements of our own director of national intelligence," Cohen said.
He continued, "[Trump] has on his team people who have contacts in and out of government that may provide insights to situations such as the Russian hacking, and while there is value in hearing multiple voices on an issue, it would be highly dangerous for the Trump administration to place a greater sense of credibility on outside voices versus the information that's collected, analyzed, assessed and validated through well-established intelligence community protocol."
ABC News' Justin Fishel and Mike Levine contributed to this report.