First, Congress, which is recessed until May 4 because of the pandemic, may have difficulty meeting if COVID-19 continues to menace Washington, D.C. Neither chamber presently has in place rules that enable it to vote remotely.
A second problem for Congress is how to handle a deadlocked state legislative vote on which presidential candidate won. If, say, a state has a presidential election that is too close to call (e.g., Florida in 2000) and its legislature cannot decide on a result, then it is not clear what happens. Each legislative chamber could send its own verdict on who won to Congress. But the 1887 Electoral Count Act (ECA) seems to say the state’s governor should choose, but legal scholars say the law is vague, and it is unclear whether Congress would need to abide by the governor’s choice and how Congress should count the submitted votes. If that were not trouble enough, some legal scholars question the constitutionality of the statute, which invites court challenges to any actions Congress takes under it. The Bush v. Gore battle of late 2000 should have spurred Congress to act. But the fight was toxic and resolved by the high court before the problems were fixed.
Third, and morbidly, Congress presently lacks a procedure to handle the death or disability of a presidential or vice presidential candidate during a contingent election. Come November, Trump will be 74 and Biden will turn 78, and will have endured a long, hard campaign. Whoever wins will be the oldest person ever elected president. If one of them or their running mates cannot serve, there are no agreed upon rules to provide a substitute candidate. Congress would be without a map for proceeding, and the selection of the president delayed for months.