In recent history, the Bush/Gore election in 2000 was polled to be close, and ended up being decided by the Supreme Court.
These are the top 5 closest elections in US history:
https://www.britannica.com/list/5-remarkably-close-us-presidential-elections
The 2000 election is worth digging into because it was straight up stolen. Bush would have lost had Florida not forced counties to stop tallying votes early (and having a law that says NO votes will count unless they ALL were tallied).
The story is scummy for even GOP standards.