“Rigged” is an opinion.
I don’t think it was rigged, but people routinely claim that due to the way the Electoral College works, all presidential elections are “rigged” in favor of the GOP. Similar claims have been made of recent Democratic primaries. Or that elections are rigged in favor of wealthy candidates, or incumbents.
Courts aren’t going to decide whether it’s true that something is “rigged”, they need something more concrete.
“Often” is an opinion about something that has happened. Just like “a lot”.
Suppose I said “Boeing aircraft often fail” and you haven’t kept up with the news. You can conclude that they have failed, but you won’t know how many times unless you ask more questions.