How can a trial get underway without that specific element of the charge being clearly stated.? It is like being prosecuted for tax evasion but without stating what exactly you did to evade your taxes.

"We will start your trial and see where it leads" sounds unconstitutional to me.

Nah. The prosecution has to disclose many things. They have to disclose their witnesses, they have to disclose all their evidence. They have to disclose any exculpatory evidence they've uncovered, even though they aren't going to use it. They have to make all those people and things available to the defense for examination and deposition.

But it's not like they have to let the defense have access to their legal theories, or their list of questions for the witnesses, or their strategies (nor vice versa). As a prosecutor, I don't have to let the defense see my opening statement ahead of the trial. I don't have to tell you my arguments in advance.

Though after pre-trial motions, there's not going to be any surprises. The prosecution only has to tell you the charges and provide you with the evidence, it's true - but if the alleged criminality isn't obvious from those materials, it will get hashed out in pre-trial motions. You will go to the judge and say, "I didn't commit tax evasion" - and if it's not obvious from the indictment how you committed tax evasion, the government will have to tell the judge why the evidence supports the charge. Or the judge will dismiss the charges.

That's what happened here. The defense went to the judge and said there's no crime here, and the prosecution had to respond. The only remaining ambiguity results from the fact that the prosecution has multiple crimes that they allege Trump's actions were in furtherance of. Trump's team knows what all the possibilities are. The judge has already held legal hearings on all of them (and ruled three of the four are valid "object crimes" under the statute). Critics of the prosecution like to characterize their disagreement over these theories as puzzlement over the prosecution's strategy, but that's no longer really the case. We know that the prosecutions possible object crimes are. The defense doesn't know which of those crimes the prosecution might decide to argue to the jury. It could be any one of them, or it could be all three. The prosecution doesn't have to tell them in advance. They don't even have to decide in advance - they can make a judgment call the day of testimony not to ask Michael Cohen about his taxes. And that's not unconstitutional.