More smoke but no smoking gun.

Michael Flynn's guilty plea Friday revealed a new layer of lies unearthed by the far-reaching investigation into ties between President Donald Trump and Russia, and put heightened scrutiny on the president's son-in-law, Jared Kushner. But Flynn's admission, and all of the criminal cases thus far, have not resolved the fundamental question special counsel Robert Mueller is seeking to answer: Did Trump's campaign collude with Russia to win the election?

Trump himself was eager to settle that question as he offered his first public response to Flynn's plea, saying Saturday: "What has been shown is no collusion, no collusion. There's been absolutely no collusion."

But Mueller has left no doubt that his investigators have amassed a wealth of knowledge about the contacts between Trump associates and the Russians, and they're looking to gather more facts from Flynn, a new key cooperator.

By forcing Flynn's assistance, Mueller gains someone who can put him in the room with Trump and his closest advisers during the campaign, transition and the early days of the administration, times when Trump associates have acknowledged communicating with people connected to Russia.

In the hours after Flynn admitted lying about his contacts with a Russian government official , two names surfaced as integral players in his actions.

Kushner was identified as a "very senior" transition official, who directed Flynn to contact foreign governments, including Russia, about a U.N. Security Council resolution last December. And KT McFarland, who served as Flynn's deputy national security adviser, was a "senior" transition official involved in discussions with Flynn about what to relay to Sergey Kislyak, then Russia's ambassador to the U.S., about the response to U.S. sanctions levied by the Obama administration.

Kushner and McFarland weren't named in court papers. But McFarland's involvement was confirmed by two former transition officials who spoke on condition of anonymity because they weren't authorized to publicly discuss the matter. One of the officials confirmed Kushner's involvement.

Flynn became the fourth person known to have been charged in Mueller's probe and the second, after former campaign policy adviser George Papadopoulos, to cooperate with investigators.

For both Flynn and Papadopoulos, prosecutors employed a similar, and textbook, strategy by accepting a limited guilty plea and turning the defendants into government cooperators.

Papadopoulos and Flynn both pleaded guilty to lying to the FBI about their foreign contacts but not for their underlying conduct.