or disfavoring a political party under the totality of circumstances under subparagraph (A), a redistricting plan shall be deemed to have the effect of unduly favoring or disfavoring a political party if— (i) modeling based on relevant historical voting patterns shows that the plan is statistically likely to result in a partisan bias of more than one seat in States with 20 or fewer congressional districts or a partisan bias of more than 2 seats in States with more than 20 congressional districts, as determined using quantitative measures of partisan fairness, which may include, but are not limited to, the seats-to-votes curve for an enacted plan, the efficiency gap, the declination, partisan asymmetry, and the mean-median difference, and (ii) alternative plans, which may include, but are not limited to, those generated by redistricting algorithms, exist that could have complied with the requirements of law and not been in violation of paragraph (1). (3) Determination of intent For purposes of paragraph (A), a rebuttable presumption shall exist that a redistricting plan enacted by the legislature of a State was not enacted with the intent of unduly favoring or disfavoring a political party if the plan was enacted with the support of at least a third of the members of the second largest political party in each house of the legislature. (4) No violation based on certain criteria No redistricting plan shall be found to be in violation of paragraph (1) because of partisan bias attributable to the application of the criteria set forth in paragraphs (1), (2), or (3) of subsection (a), unless one or more alternative plans could have complied with such paragraphs without having the effect of unduly favoring or disfavoring a political party. (c) Factors prohibited from consideration In developing the redistricting plan for the State, the independent redistricting commission may not take into consideration any of the following factors, except to the extent necessary to comply with the criteria described in paragraphs (1)