A complex set of checks and balances developed between these three branches. For example, the assemblies theoretically held all power, but were called and governed by the magistrates, who, controlling discussion, exercised dominating influence over them. Other magistrates could also veto proceedings before the assemblies, though until the late republic, this was rare. Similarly, to check the power of the magistrates, each magistrate could veto one of their colleagues and the plebeians elected tribunes who could intercede and veto the actions of a magistrate.