illustrate exactly how they were trying to undo the established electoral certification process, including the completion of the Certificate of Ascertainment, by declaring the election "fraudulent" and citing this -
Article II
Section 1.
The executive power shall be vested in a President of the United States of America. He shall hold his office during the term of four years, and, together with the Vice President, chosen for the same term, be elected, as follows:
Each state shall appoint, in such manner as the Legislature thereof may direct, a number of electors, equal to the whole number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or person holding an office of trust or profit under the United States, shall be appointed an elector.
https://www.law.cornell.edu/constitution/articleii
Thus, per their claim, they could essentially deputize state legislatures (except if they were controlled by Democrats

) to "select the electors" and decide on the outcome.
Of course they forgot that years ago, all of the state legislatures passed laws on how to conduct Presidential elections, including creating a delegation-of-authority position of "Secretary of State" (in most states), where one of that position's duties was to oversee elections in general, including the selection of Presidential electors.
So given these facts, it would end up with their need to consider some ex post facto law to overturn procedures that were already put in place and had been used for decades. But since they were cherry-picking which states to do this with, it made what they were attempting to do even more ludicrous.
This is a copy of PA's Certificate of Ascertainment -

as tweeted by the National Archives -
TEXT
US National Archives
@USNatArchives
Additional Certificates for Ascertainment have been posted to
https://archives.gov/electoral-college/2020
Alabama
Michigan
Pennsylvania
South Dakota
#ElectoralCollege #Election2020
📸 Page 1 of Pennsylvania Certificate of Ascertainment
Image
9:20 AM · Nov 27, 2020
Here is NARA's link to all of the Certificates -
https://www.archives.gov/electoral-college/2020