Cohen pleads guilty for lying to Congress
Other than Cohen lying, and the possibility (not the fact, just the possibility) of some sort of business quid pro quo attempt by the Russians, there's nothing here about the election or collusion. It's a minor lie about a business deal that never happened. Stupid for Cohen to lie about it, criminal for him to lie about it to Congress, but I don't see cause to panic about Russian Collusion here.
That might change if the content of those conversations contained something nefarious, but there's no indication here of anything more than a business deal that didn't happen.
Mueller will probably focus on the January 20th call to Cohen. That's Trump's inauguration date and the call was supposedly from the Russian President. It seems more likely to be a political/diplomatic call than one about a business deal.
It's worth noting that this is yet another case of Mueller creating a process crime. Cohen is not pleading guilty to collusion, or to any illegal act in and of itself. He's pleading guilty to lying to Congress about communications concerning a business deal that didn't happen. Yeah, he shouldn't have lied about it -- and that's assuming it wasn't a case of "lying" like Mike Flynn "lied". But without Mueller's investigation, there would be no crime here.
The real question here is: what did Trump's written answers say on these topics? Cohen is only pleading guilty after those answers were completed and returned. Will Mueller claim Trump is lying in those answers based on a contradiction with Cohen's testimony? That's my guess about where this is going: Mueller either will do that, or is frustrated about not being able to do it. The latter guess is because of the kerfluffle about Manafort's joint defense agreement with Trump.
Reading tea leaves... I think Trump gave correct, accurate, answers and Mueller is claiming the scalps he can claim. Cohen for lying to Congress, and whatever he can get against Manafort for letting Trump know what Mueller was trying to catch him out for.
UPDATE: Looks like my tea leaves are accurate.
UPDATE: It's probably worth noting that, despite Cohen's guilty plea (presumably under pressure from Mueller), the document describing how he lied is subject to interpretation. For example, Cohen is said to have lied about never agreeing to travel to Russia as part of the deal. He discussed hypothetical travel, and in fact, never agreed to actual travel, just to schedule ideas for a hypothetical trip. Similarly, how much involvement is "limited" involvement? One briefing? Two? Three? Over a year or two?
Cohen pled guilty to lying, but it's not at all clear to me from the evidence laid out that he actually did.
UPDATE: Mueller left out exculpatory information.