I don’t think he can because the RNC already happened making him the party’s nomination. The DNC hasn’t happened yet so the Democrats were able to switch candidates before they meet to nominate.
https://ballotpedia.org/ State laws and party rules on replacing a presidential nominee, 2024
She talks about laughing on some podcast but I can’t remember which one. Anyway, she said that most comics don’t really haha/laugh out loud at great jokes, but will simply say that’s a great joke with approval. So being the host on tv she is having to train herself to laugh at loud at things. The show is scripted and the footage cut up post filming so some people/contestants are funnier but they couldn’t air it or their words were tempered by the writers/editors. Here’s one interview podcast with her and Conan https://youtu.be/qDkFXrS-P-8?si=t9MqFHltXbSm0ccG