Well, for what it's worth (no comments please!), I think if a vote is seriously believed to have been rigged, it should be thoroughly investigated and exposed as such; if a different outcome would have altered the election outcome, the people should be encouraged to vote again.
However, the reality is that those saying it was rigged are likely to be booed off as 'sore losers'. There would have to be decent grounds before an investigation was started and it would need to yield some hard evidence pretty quick. That would be difficult.
So, regardless of rights and wrongs, I don't believe it will happen.