Assume that President Donald Trump is impeached and removed from office. At that point, Mike Pence would become president. The position of vice president would remain vacant until Congress confirmed a replacement, nominated by the president.
This shift in positions could result in a very unlikely possibility: If, prior to the confirmation of a new vice president, President Pence were to become unable to discharge the office, then Nancy Pelosi, the speaker of the House, would assume the office of the president under the Presidential Succession Act of 1947.
Or would she? Two prominent constitutional-law professors contended in 1995 that the Succession Act now in force is unconstitutional. And a recent New York Times op-ed agreed: Legislators, such as the speaker of the House, cannot be elevated to the presidency, the thinking goes.
This theory, if correct, risks throwing the United States and the entire free world into a state of chaos. The speaker and the secretary of state (the next-in-line, nonlegislative officer) could both claim, with some legitimacy, to be president. Bush v. Gore would be tame by comparison.