The Grand Jury brings the indictment. The indictment is for the falsification of records charge, 175.10. That charge requires an "underlying crime".
The indictment did not specify the underlying crime. It is supposed to, but leaving it out can be remedied by a "Bill of Particulars" under NY law.
So that was provided to the defense, and there were 4 possible underlying crimes that were identified by the prosecutors last May.
Those 4 theories were reviewed by the judge, who said that as long as the evidence presented to grand jury supported any of the underlying crime theories, that would be good enough to save the indictment
The judge ruled that the grand jury had seen enough evidence to support 3 of the 4 possible theories advanced by the DA's office. The 3 survivors were The Federal Election Campaign Act, New York Tax law 1801(a)(3) and 1802, or New York Election law 17-152.
He precluded the 4th theory because the evidence shown to the grand jury was insufficient to allege that crime. (It was a repetition of the records charge, in some weird logic)
Anyway, the prosecution settled on the election law 17-152 as their primary theory, and that's where we are now. They are trying to prove a "conspiracy to promote or prevent an election"
§ 17-152. Conspiracy to promote or prevent election.
Any two or more persons who conspire to promote or prevent the election of any person to a public office by unlawful means and which conspiracy is acted upon by one or more of the parties thereto, shall be guilty of a misdemeanor.