Sen. Sheldon Whitehouse of Rhode Island, the ranking member of the Senate Crime & Terrorism Subcommittee, addressed the "peculiar behavior" behind President Donald Trump's "warm embrace" of former national security adviser Mike Flynn.

"[Flynn] lied to a lot more than the Vice President," said Whitehouse on MSNBC's "All in with Chris Hayes." "There's a very good chance he lied to the FBI during the interview ... that's a lot going on in the White House."

However, prior to former Deputy Attorney General Sally Yates' testimony before the Senate Judiciary subcommittee on Monday, Trump went to Twitter to defend Flynn's hiring — despite reportedly being warned by former President Barack Obama against bringing Flynn into his administration. "General Flynn was given the highest security clearance by the Obama Administration," Trump said, "but the Fake News seldom likes talking about that." Trump tweeted.

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27 PHOTOS Key Trump officials, advisers of note in the Russia probe See Gallery Key Trump officials, advisers of note in the Russia probe Tom Barrack The close friend to Donald Trump and CEO of private equity firm Colony Capital recommended that Trump bring in Paul Manafort for his presidential campaign. R. James Woolsey Woolsey, the former director of the Central Intelligence Agency (CIA), has cooperated with Mueller's investigation and worked with Michael Flynn and was present at a meeting where they discussed removing the controversial Turkish Muslim cleric Fetullah Gulen from US soil. (Christopher Goodney/Bloomberg via Getty Images) The former senior Trump campaign official and White House adviser was present and crucial during the firings of Michael Flynn and James Comey. The former head of the Trump transition team following the 2016 election has said previously that he believes he was fired due to his opposing the hiring of Michael Flynn as national security adviser. Jeff Sessions Former U.S. senator Jeff Sessions from Alabama joined Trump's campaign as a foreign policy adviser in February 2016. Sessions was nominated to be U.S. attorney general by President Trump and was then confirmed by the Senate. Reports then emerged that Sessions had spoken twice with Sergey Kislyak while he was senator -- a fact that he left out of his Senate hearing testimony. Instead, he said in writing that he had not communicated with any Russian officials during the campaign season. Sessions defended himself saying he had spoken with Kislyak specifically in a senate capacity. Paul Manafort Paul Manafort signed on as Donald Trump's campaign manager in March 2016. A longtime Republican strategist and beltway operative, Manafort had previously served as an adviser to former Ukrainian president Viktor Yanukovich -- a pro-Russia leader who was violently ousted in 2014. Manafort resigned from his campaign position in August 2016 amid questions over his lobbying history in Ukraine for an administration supportive of Russia. The former campaign manager reportedly remained in Trump's circle during the post-election transition period. Michael Flynn Gen. Michael Flynn was named President Trump's national security adviser in November of 2016. Flynn reportedly met and spoke with Russian Ambassador Sergey Kislyak in December, at one point discussing sanctions. Flynn originally told Vice President Pence he did not discuss sanctions -- a point the Department of Justice said made the national security adviser subject to blackmail. Flynn resigned from his position in February. Donald Trump 2016 election winner Donald Trump is at the center of special counsel Robert Mueller's probe into Russia's handlings. Sam Clovis Clovis, a former member of the Trump campaign, arrives on at the U.S. Capitol December 12, 2017 to appear before a closed meeting of the House Intelligence Committee. Clovis worked with George Papadopoulos, a former Donald Trump campaign foreign policy advisor who struck a plea deal on charges of lying to the FBI. (Photo by Win McNamee/Getty Images) Roger Stone Stone is a longtime Republican political consultant who served as a campaign adviser to Trump who continued to talk with the then-GOP candidate after stepping away from his adviser role. Stone claimed last year that he had knowledge of the planned WikiLeaks release of emails pertaining to Hillary Clinton and the Democratic National Committee. Stone recently admitted to speaking via direct message with "Guccifer 2.0" -- an online entity U.S. officials believe is tied to Russia. Stone says the correspondence was “completely innocuous.” Carter Page Page worked for Merrill Lynch as an investment banker out of their Moscow office for three years before joining Trump's campaign as a foreign policy adviser. During his time with Merrill Lynch, Page advised transactions for two major Russian entities. Page has called Washington "hypocritical" for focusing on corruption and democratization in addressing U.S. relations with Russia. While Page is someone Trump camp has seemingly tried to distance itself from, Page recently said he has made frequent visits to Trump Tower. J.D. Gordon Before Gordon joined the Trump campaign as a national security adviser in March 2016, he served as a Pentagon spokesman from 2005 through 2009. Like others involved in Trump-Russia allegations, Gordon met with ambassador Kislyak in July at the Republican National Convention, but has since denied any wrongdoing in their conversation. He advocated for and worked to revise the RNC language on and position toward Ukraine relations, so it was more friendly toward Russia's dealings in the country. Former Trump campaign aide Michael Caputo (L) Caputo waves goodbye to reporters after he testified before the House Intelligence Committee during a closed-door session at the U.S. Capitol Visitors Center July 14, 2017 in Washington, DC. Caputo resigned from being a Trump campaign communications advisor after appearing to celebrate the firing of former campaign manager Corey Lewandowski. Denying any contact with Russian officials during the 2016 campaign, Caputo did live in Moscow during the 1990s, served as an adviser to former Russian President Boris Yeltsin and did pro-Putin public relations work for the Russian conglomerate Gazprom Media. (Photo by Chip Somodevilla/Getty Images) Stephen Miller, White House Senior Advisor for Policy Jason Miller Former White House Press Secretary Sean Spicer Eric Trump Donald Trump Jr. Ivanka Trump White House Senior adviser Jared Kushner Executive assistant to Donald Trump Rhona Graff White House Communications Director Hope Hicks Former Trump campaign manager Corey Lewandowski US Vice President Mike Pence Katrina Pierson K.T. McFarland Former White House Communications Director Anthony Scaramucci Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

"It suggests that there is some sensitivity to Russia in this White House that prevents them from reaching obvious conclusions, like 'My national security advisor may be compromised, let's firewall the guy till we get to the bottom of this,'" said Whitehouse.

"I don't know if they're trying to send a signal to him, if they're afraid that he is cooperating or might be cooperating and they want to kind of calm him down," continued Whitehouse. "I don't know what that is all about. It doesn't make obvious sense."

Flynn was fired after 24 days in the Trump administration after The Washington Post reported that he had lied to Vice President Mike Pence about his discussions between Russian ambassador Sergey Kislyak. Before he was dismissed; however, several news outlets reported that Yates had informed White House staff of Flynn's false statements — potentially exposing Flynn to blackmail by the Russian government.

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SEE ALSO: 'He could be blackmailed by the Russians': Sally Yates explains why she warned the White House about Michael Flynn