In which case did the Supreme Court rule that state courts could not interfere with Senate elections?

The Supreme Court ruled that state courts could not interfere with Senate elections in the case of Bush v. Gore. This landmark decision arose from the contentious 2000 presidential election, particularly focusing on the Florida recount. The Court determined that the methods used for the recount violated the Equal Protection Clause of the Constitution, as different counties in Florida employed varying standards for counting votes. The crux of the ruling emphasized that state courts could not impose their own procedures that would disrupt federal election processes, including Senate elections.

This ruling clarified the separation of state and federal jurisdiction in the realm of elections and underscored the importance of uniformity in the electoral process, thereby helping to uphold the integrity of elections governed by federal law.