Beyond media spin and promoting falsities, is it possible for US elections to be rigged?

[VCU for Ron Paul]

Is it at all even remotely feasible that a candidate, whoever it is, can win an election, be it at whatever stage.. through means other than having the greatest support and number of votes? We've all seen throughout history the amount of fraud, attempted fraud and scandals involved in various elections including the presidency. While I'm not extremely well versed in the whole ordeal in Florida in 2000, that is the most recent major controversy (yes?), obviously it didn't go swimmingly and there are still strong disagreements in it's regard.

What further checks and balances or systems have we implicated in the United States to make sure something like this is far less likely to occur?

This is of course all stemming from genuine curiosity and I do not have time right now to do my own research because Calculus is kicking my ass and I have an exam tomorrow. :/

Any information or opinions appreciated, thanks.

[Merk]

http://blackboxvoting.org/

[sailingaway]

There are convictions for voter fraud periodically, so clearly to some extent yes. However, it is generally marginal. Voter machines have the POTENTIAL to be rigged, but various states have various protections. And primaries aren't seen as regular elections. Ron was denied his delegates in Nevada last time, etc. Courts don't interfere much in how a party chooses its nominees which seems wrong since they have a legally protected monopoly in all real senses of the term. However, parties do care about credibility.