First, yes they will be re-ran, and it's doubtful the winning candidate will even get to run. Also, where does it end, do we keep re-running it until we get the right candidate? What if it was the candidate you voted for, how would you feel?
Second, yes apparently you can, it happened. If the whole country was able to be swayed by TikTok ads but apparently no politicians noticed then they aren't very good at politicking or governing. If they noticed an issue they should have dealt with TikTok earlier.
So far TikTok hasn't been held liable, only the voters who choose to vote for this candidate.