The opposition candidate acknowledges that Chavez won, but questions the margin. That seems like a reasonable position.
Even if there was not direct fraud, eg rigged voting machines, the political situation is quite polarised and certainly people can feel intimidated one way or the other.
Though it would not be anti-democratic to remove the limit of two presidential terms, I still think it would be a bad idea because the person-centered type of politics has not really been beneficial to South America so far.