The Constitution of the United States provides several basic requirements for eligibility to be elected to the office of President. Individual states did not introduce significant relevant legislation until Barack Obama was elected in 2008. The controversy generated by various conspiracy theorists who asserted during the 2008 presidential election campaign that Obama was not a natural-born U.S. citizen, as mandated by the Constitution, and thus was ineligible to be President of the United States, prompted several state legislatures to consider legislation aimed at requiring future presidential candidates to show proof of presidential eligibility before being granted ballot access in their state.