Will addressing the constitutionality of the Westfall Act lead to the end of the two party system?
It may be a contributing factor.
What could make the U.S. Supreme Court divided over an interpretation other than party perspective? The Supreme Court is considered tied now, with four conservative justices and four liberal justices, and the winner of the 2016 presidential election had the capacity to sway Supreme Court decisions for decades. The decisions made by the Supreme Court are political, which means that the court is evolutionary, based on where America is along the evolutionary scale, and we can evolve or devolve based on their decisions.
For America to evolve to the next level, we must start to address a higher form of electing our government officials, and let go of the two party system. Candidates for any elected position must be functioning based on what is in everyone's best interest.