The recount underway in Pennsylvania’s U.S. Senate race marks the end of a chaotic post-election period that has become the latest example of how disputed election rules can expose weak points in a core function of American democracy.

Pennsylvania Gov. Josh Shapiro has agreed with the state’s Supreme Court that ruled certain mail-in ballots shouldn’t be counted. Shapiro,

Pennsylvania's state Supreme Court on Monday weighed in on a flashpoint amid ongoing vote counting in the U.S. Senate election between Democratic Sen. Bob Casey and Republican David McCormick, ordering counties not to count mail-in ballots that lack a correct handwritten date on the return envelope.