The Hartford Convention

First, I believe GOD caused them to vote to stay in.

Second, same for the Confederacy, had it succeeded in becoming a separate nation...they likely woulda tried to get back in before long, as they woulda faced a hostile US who wouldn't want to trade with them, & they weren't strong enough on their own to have kept the British or French out, & when an invasion threatened, they'da come crawling back, begging the US to re-admit them.