Supergirl season 4 has launched to dramatic effect, with the world learning at last that President Olivia Marsdin is actually a shapeshifting alien. Viewers have known this for over a year now, but the revelation couldn't have come at a worse time, or been done in a more damaging way. Marsdin was outed by anti-alien extremists, confirming a conspiracy theory that has apparently been circulating in hate groups online for years.
Kara Danvers is typically an optimist, but even she'll be challenged by what comes next. The United States will be plunged into an unprecedented constitutional crisis, and everything that President Marsdin has accomplished during her presidency will be called into question.
The first issue is the question of whether or not Marsdin is a legitimate president in the first place. Article 2, Section 1, Clause 5 of the United States Constitution states: "No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty-five Years, and been fourteen Years a Resident within the United States." Marsdin is secretly a Durlan, and - until her presidency - there have been no legal routes for extraterrestrials to become US citizens in Supergirl's world. She will almost certainly have to explain herself in a speech, and then step down. That will even have a personal impact upon Supergirl, who's been strongly associated with Marsdin and will be tarnished by association in the eyes of the public (the season 4 premiere showed that Kara had open, unrestricted access to the Marsdin White House).
Worse, President Marsdin's entire political agenda will then be called into question. She's personally responsible for pushing the Alien Amnesty Act, which granted aliens the rights of US citizens and created a legal route to citizenship for extraterrestrials. Now, though, that looks as though she was secretly serving the interests of her own people, rather than doing what was best for the United States. It's highly likely that the Senate will revoke the Alien Amnesty Act. Meanwhile, they'll be under pressure to ensure extraterrestrials never secretly infiltrate the highest offices of government again. It wouldn't be a surprise to see politicians push for an Alien Registration Act, requiring all aliens to register their identities with the government. That would even put pressure on the likes of Superman and Supergirl; would they choose to register, or instead break the law? If they chose the latter, Kara's partnership with the DEO would be at an end. But that might be a good thing anyway; as a new administration gradually took shape, there'd be huge political pressure to reform the DEO in accordance with the new agenda.
Meanwhile, anti-alien hate groups - like the one run by Agent Liberty - will see their membership and influence boom like never before. They'll be able to spin the outing of President Marsdin as a massive coup, as evidence that aliens have only become acceptable in American society because they systematically infiltrated every level of government. It could even be portrayed as a secret, subtle invasion; they'd argue that anyone who attacked an alien would really be a patriot, defending their country against invaders. More people will become radicalized, and there'll be a boom in the number of anti-alien hate crimes. When Supergirl and the DEO intervene, their loyalties will be called into question; are they supposed to be protecting humans from aliens, or aliens from humans? Some politicians will even demand that the DEO cease intervening in attacks on extraterrestrials, and simply focus on dealing with alien criminals. If an Alien Registration Act is indeed pushed for by the Government, the DEO will have to enforce it - or be radically restructured.
The premiere of Supergirl season 4 has seen Mercy and Otis Graves successfully open Pandora's Box. It's not hard to see where things are going; Kara's optimism is about to be challenged by the darker side of human nature, as hate and prejudice are unleashed against aliens across the world. The outing of President Marsdin may be a political act, but it's probably the most significant event in the history of the show to date. Supergirl's version of the United States can never be the same again.