It was an intriguing new clue in Robert Mueller's investigation, hiding in almost plain sight.

All thanks to a botched filing by the lawyers for Paul Manafort, Donald Trump's former

campaign manager.

The lawyers had intended to rebut accusations by Mueller's prosecutors that Manafort had

lied to them after agreeing to cooperate with the Russia investigation following his

conviction on eight counts of financial fraud last August.

The lawyers argued that Manafort should be cut some slack.

He was suffering from severe gout, depression, and anxiety, and therefore shouldn't be

punished if his memory about key events was a bit foggy.

But when they addressed the specifics of Mueller's accusations, they made a formatting error,

and sensitive material they intended to black out in their public filing was easily readable

once you downloaded it on the internet and printed it out.

It was only then when we learned what Manafort had hidden from federal prosecutors that

he had shared Trump campaign polling data with a business associate, Constantine Kalimnik,

who has been identified by US officials as a Russian intelligence asset.

Think about that.

The chairman of a major party presidential candidate is slipping internal campaign data to a

foreign adversary's intelligence source.

Is this hard new evidence of collusion between the Trump campaign and the Kremlin?

Or is it like much else in the Mueller probe yet another ambiguous piece of a very murky

puzzle?

We'll discuss with one of Washington's leading scholars of the Russia investigation,

...