College must occur on a single day throughout the country; Article I established that elections for Congressional offices, however, can be held at different times. Congressional and presidential elections take place simultaneously every four years, and the intervening Congressional elections, which take place every two years, are called midterm elections. The constitution states that members of the United States House of Representatives must be at least 25 years old, a citizen of the United States for at least seven years, and be a (legal) inhabitant of the state they represent. Senators must be at least 30 years old, a citizen of the United States for at least nine years, and be a (legal) inhabitant of the state they represent. The president and vice president must be at least 35 years old, a natural born citizen of the United States and a resident in the United States for at least fourteen years. It is the responsibility of state legislatures to regulate the qualifications for a candidate appearing on a ballot paper, although in order to get onto the ballot, a candidate must often collect a legally defined number of signatures. Presidential elections The president and the vice president are elected together in a presidential election. It is an indirect election, with the winner being determined by votes cast by electors of the Electoral College. In modern times, voters in each state select a slate of electors from a list of several slates designated by different parties or candidates, and the electors typically promise in advance to vote for the candidates of their party (whose names of the presidential candidates usually appear on the ballot rather than those of the individual electors). The winner of the election is the candidate with at least 270 Electoral College votes. It is possible for a candidate to win the electoral vote, and lose the (nationwide) popular vote (receive fewer votes nationwide than the second ranked candidate). Prior to ratification of the Twelfth Amendment to the United States Constitution (1804), the runner-up in a presidential election became the vice president. Electoral College votes are cast by individual states by a group of electors; each elector casts one electoral college vote. Until the Twenty-third Amendment to the United States Constitution of 1961, citizens from the District of Columbia did not have representation and/or electors in the electoral college. In modern times, with electors usually committed to vote