Graham asked former Director of National Intelligence James Clapper at a Senate Judiciary subcommittee hearing on Monday whether he had concerns about Russian ties to Trump's business interests.
Here are some of the biggest issues that have not been directly answered by any current or former government official.
It was more than a week after Yates raised concerns about Flynn with McGahn that the story leaked to the Washington Post, prompting a series of events that led to Flynn's ouster from his White House job. Chris Coons that in the meetings, McGahn "demonstrated that he understood that this was serious". She said during the hearing she had alerted the White House earlier this year Flynn could be "essentially blackmailed by the Russians".
Flynn resigned February 13 following reports that he had misled Vice President Mike Pence and other officials about his contacts with Russian Federation.
US President Donald Trump "welcomes" investigation into his business dealings in Russian Federation, says White House press secretary Sean Spicer, asserting that he has no business in the country.
Trump insists no evidence of collusion with Russian Federation
Trump had also used Twitter before the hearing to insinuate that Yates had leaked information on Flynn to the media. It also filled in basic details about the chain of events that led to Flynn's ouster in February.
He clarified later that he had not taken any new actions.
Graham asked Yates whether she had any information about whether there was collusion between members of the Trump campaign and Russian Federation.
"We are not going to re-litigate the past on this", Spicer said again. Yates was sacked for that decision. She told the committee that she sought to meet with White House officials as "a matter of some urgency" after seeing the intelligence intercepts.
This time, the surprise wasn't so much about what the president as it was about where how he said it.
After former Acting Attorney General Sally Yates and former Director of National Intelligence James Clapper testified on Capitol Hill Monday, President Trump took to Twitter to dismiss their revelations. What exactly did Flynn say to the Russian ambassador to the United States?
Trump touts Australia's health system (to Bernie Sanders' delight)
He added that Americans will have a "great" system soon, referring to the just-passed House of Representatives health care bill. Earlier on Friday afternoon, White House spokeswoman Sarah Huckabee Sanders sought to downplay Trump's comments to Turnbull.
The conversation took place two days after the Federal Bureau of Investigation interviewed Mr Flynn about those contacts.
Some Republicans veered away from questions about Russia's alleged involvement in the election to focus on issues such as whether Obama administration officials had improperly revealed the names of Trump administration officials contained in surveillance records.
Did Flynn break any laws and, if so, will he face criminal charges?
Ms Yates told the hearing: "We felt like it was critical that we get this information to the White House, in part because the vice president was making false statements to the public and because we believed that General Flynn was possibly compromised".
Graham also said he wants to hear from former Obama national security adviser Susan Rice, who declined to appear at Monday's hearing, to determine whether she was involved in the unmasking of any Americans. Flynn had said that he didn't talk about sanctions.
National monuments a 'massive federal land grab'
These designations, critics argue, hinder American enterprise from exploiting potentially valuable land resources. Rescinding or altering a national monument designation would be new ground for the government, he said .
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