Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.) on Thursday piled onto ongoing questions about President Trump and his associates' ties to Russia.

Days after the FBI confirmed it is probing any possible cooperation between Trump's team and Moscow, Sanders implied Russian President Vladimir Putin might "have" something on the president.

How does it happen that we have a president who has nothing but nice things to say about Mr. Putin? What do the Russians have on Mr. Trump? — Bernie Sanders (@BernieSanders) March 23, 2017

Questions about Trump and his current and former aides' potential ties to Russia have roiled his administration in its first two months. The president's first national security adviser, Michael Flynn, resigned after it was revealed that he discussed sanctions with Russian Ambassador Sergey Kislyak before Trump took office.

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And Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsTrump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status White House officials voted by show of hands on 2018 family separations: report MORE has also come under scrutiny for failing to disclose the fact that he twice met with Kislyak while he was acting as a surrogate for Trump's election campaign last year. He recused himself from any federal investigations into Russian election meddling and the Trump campaign last month.

Sanders's questions followed House Intelligence Committee Chairman Devin Nunes's (R-Calif.) announcement Wednesday that he had seen evidence that the intelligence community incidentally gathered information on Trump transition team members during routine surveillance of foreign targets.

Nunes said, however, that the intelligence collections had "nothing to do with Russia and nothing to do with the Russian investigation."

The intelligence community has concluded that Putin was behind Russian efforts to interfere in the U.S. election in order to help Trump's campaign.

The FBI is currently investigating the Kremlin's election meddling, as well as potential links to Trump's team, Director James Comey confirmed at a House hearing on Monday.

Trump has repeatedly denied any relationship between himself or his campaign and the Russians, and has called media reports on the matter "fake news."

Trump has spoken fondly of Putin on multiple occasions, saying at one point that he is a stronger leader than former President Barack Obama Barack Hussein ObamaThe Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon Trump appointees stymie recommendations to boost minority voting: report Obama's first presidential memoir, 'A Promised Land,' set for November release MORE and expressing a willingness to cooperate with Russia on certain issues, such as fighting the Islamic State in Iraq and Syria.