They know we know, but they can't help themselves. Like the Wicked Witch, the Democrats are in a mental feedback loop. For them, the night of November 8, 2018 never ended. They can't get over the election and so they will run on impeaching President Trump no matter how much it will hurt their chances of winning. Hopefully, they never get over it.
If the left were rational this would be a heads up. They are not. they believe the Trump component of culture is stupid and immoral. They treat everything that comes out of Trumpism with absolute contempt. Telling them the truth immunizes them from the truth. They will never accept their failings because their commitment is absolute and unwavering. They are leftist zealots who would sooner die than admit they are wrong.