The Constitution requires the President of the United States to take the following oath of office:
I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States.
There can no longer be confidence that Donald Trump, the winner of the electoral vote tally on election night, can fulfill this oath. Because a foreign agent cannot possibly faithfully execute the office of President of the United States.
Russia has now openly admitted that they have been in secret contact with the Trump campaign, giving them help. While Trump himself had adamantly denied that before the election, but has been mute on the subject since the election, proving that the Trump campaign was as much a red meat con as Trump Steak.
Rachel Maddow covered this in depth on Thursday night:
Donald Trump, as the president-elect, is now privy to the Presidential Daily Brief, which means that Vladimir Putin very well might be, too.
There are now reports that the White House is reviewing the Dworkin Report, clearly outlining the incoming Oval Office occupant's ties to Russia after the same FBI that injected itself into the election with 10 days to go with an email nothingburger hurriedly tried to clear Trump.
This is not just someone being friendly to another country. This is Russia assisting a candidate for president with hacks and more, and revealing and reveling in those connections after that candidate won.
Donald Trump, at the very least, owes his election to Putin. At the most, he and his top aides are working at the behest of Putin. Either way, a president who cannot and has no intention to actually be faithful to the United States cannot be a legitimate president. And yet, he won the electoral tally.
And that's a Constitutional crisis.