The quote is just another Schiff lie. He says:
““The argument, ‘why don’t you just wait?’ comes down to this: Why don’t you just let him cheat in just one more election?” Schiff stated. “Why not let him have foreign help one more time?”
Obviously, Mueller found no collusion the first time. It is more “exaggeration”. And they cannot prove and do not even demonstrate any attempt at cheating in regards this impeachment claim (though they may draft it in the final resolution).
And as others have pointed out, they don’t want to go down that road because if they do impeach him for “investigating Biden” that opens the door wide open for the Senate to investigate whether Biden deserved being investigated. And that leads to revealing all kinds of other corruptions! They desperately want to avoid justifying any digging in the rabbit hole.
But they have boxed themselves in on this. They are going to lose if these are the articles, and after it is all settled they will be out of gas and Trump will deliver the well deserved political payback.
As an aside, this comment was made at a press conference and I would think, therefor, is not protected by the Speech and Debate Clause. In theory, Schiff opened himself up to a defamation lawsuit by asserting he “cheated” when the entire Mueller investigation showed no evidence that he did.