Presidential succession in the United States is governed by the 25 th Amendment to the Constitution, which provides that the Vice President "shall become President" should the incumbent chief executive die, resign, or be removed from office. The new President then nominates a successor Vice President, subject to confirmation by a majority vote of both houses of Congress. In the event there is neither a President nor a Vice President, the Presidential Succession Act provides that the Speaker of the House of Representatives, the President pro tempore of the Senate, and duly-confirmed Cabinet officers, in order of the seniority of their departments, would be eligible to act as President. These provisions apply at all times when a duly-sworn President or Vice President holds office, but additional factors enter the equation during presidential election years. The three-to-four month period of the presidential general election campaign, from the national party conventions through election day, and the 10-week transition period, from election day to the January 20 inauguration, present a different range of succession issues concerning presidential and vice presidential nominees during the campaign and the President- and Vice President-elect during the transition. This situation is further complicated in elections when an incumbent President who is retiring or who has failed to win reelection prepares to leave office, while the incoming President-elect prepares for inauguration. It should be noted, however, that the period preceding the inauguration of Presidents who have been elected to a second consecutive term does not generally fall under the definition of a presidential transition. For instance, the period between President Barack H. Obama's election to a second term on November 6, 2012, and his inauguration on January 20, 2013, was not a transition period as defined in this report. For the purposes of this report, "presidential election campaign" refers to the period between the national party nominating conventions, traditionally held in July or August of the election year, and election day, the Tuesday after the first Monday in November, which falls on November 8 in 2016. In modern times, the transition period is considered to start immediately after the general election, and extends through January 20 of the following year. The first part of the transition period extends from election day through the meeting of the electoral college, which, for the 2016 election, takes place on December 19. During this period, with few exceptions, the winning candidates are known on the basis of the popular vote tally and the projected electoral vote results. They are "heirs apparent," the de facto President- and Vice President-elect. The transition's second phase begins when the electors cast their votes and the electoral vote is announced. At this point, the balance of scholarly opinion holds that the candidates who received a majority of electoral votes actually become the President- and Vice President elect. This report examines succession procedures that apply to major party nominees for President and Vice President during the presidential election campaign and the first phase of the transition period, and for President-elect and Vice President-elect during the second phase of the transition period. Presidential transitions in the past half-century have generally been characterized by high levels of activity and frequent improvisation as the President-elect's team works to finalize personnel and policy arrangements for the incoming administration within a period of just over 10 weeks. The process takes on further significance and complexity when, as noted previously, a new President replaces a retiring or defeated incumbent, or when political party control of the executive branch also changes. Succession and disability procedures concerning the President-elect and Vice President-elect provide a potential complicating factor during the election period and the transition. They are based on a combination of political party rules, federal law, and constitutional provisions, different elements of which apply at different times during the whole period between the national conventions and inauguration of the incoming chief executive. Depending on circumstances, Congress could be called on to make succession-related decisions of national importance in questions of the death, disability, or resignation of a President- or Vice President-elect. Vacancies in a major national party ticket during the presidential election campaign, which extends roughly from the party nominating conventions through election day in November, are covered by the rules of the political parties. Although it might be assumed that the vice presidential candidate would succeed in the event of a vacancy in the presidential nomination, in fact, both major parties provide for replacement by their respective national committees. Procedures established by the Democratic and Republican parties are detailed below. The Charter and By-Laws of the Democratic Party provide that vacancies on the presidential ticket would be filled by a special meeting of the Democratic National Committee (DNC). Voting in the DNC would be per capita by individual members; a majority of members present and voting would be necessary to nominate a successor candidate. The Rules of the Republican Party provide that vacancies on the presidential ticket could be filled either by the Republican National Committee (RNC), or by the national convention, which could be reconvened at the call of the committee. Voting in the RNC would be by state, with the three committee members in each state delegation casting the same number of votes as the number of delegates assigned to it during the previous national convention; a majority of the votes cast would be necessary to nominate a successor candidate. The most recent example of filling a vacancy in a major party presidential ticket occurred in 1972, when the Democratic vice presidential nominee, Senator Thomas F. Eagleton, resigned from the ticket on August 1. The party's presidential nominee, Senator George McGovern, selected former Ambassador R. Sargent Shriver to fill the vacancy, and on August 8, a special meeting of the Democratic National Committee confirmed the nomination. An earlier precedent occurred in 1912, when Vice President James S. Sherman, Republican President William H. Taft's running mate, died on October 30, just days before the November 5 general election. The Republican National Committee nominated Columbia University President Nicholas M. Butler to replace Sherman, and all eight Republican electors subsequently voted for Butler. Sherman's death and the ensuing vacancy had no influence on the outcome of the election, and Butler's appointment proved to be noncontroversial because Taft came in last in the three-way presidential election: former President Theodore Roosevelt had quit the Republican Party to run as the candidate of his own Progressive Party, thus splitting the Republican vote. Consequently, Democratic nominee Woodrow Wilson won with a 41.8% plurality of the popular vote, but a very large electoral college majority of 435 electoral votes to 88 for Roosevelt and eight for Taft. Presidential transitions are generally considered to begin immediately after election day. Throughout the first phase of transition, which lasts through the meetings of the electoral college, the winning candidates are considered to be the next President and Vice President, but their status is informal and presumptive. It should be noted that there actually is no President- or Vice President-elect until after the electoral votes have been cast. The apparent winners, during this first period, are still the nominees of their parties. The use of the titles "President-elect" and "Vice President-elect" is a time-honored courtesy that anticipates the ultimate status of the candidates who won an apparent majority of electoral votes. If a vacancy happens in either position during this period, most commentators suggest that the political parties would follow their long-established rules, as detailed earlier in this report. In the event of the presidential nominee's death, it might be assumed that the vice presidential nominee would be chosen, but neither of the major parties requires this in its rules. Further, it is assumed that the electors, who are predominantly party loyalists, would abide by the national party's decisions. Given the unprecedented nature of such a situation, however, confusion, controversy, and a breakdown of party discipline among the members of the electoral college might also arise, leading to fragmentation of the electoral vote. For instance, an individual elector or group of electors might justifiably argue that they were nominated and elected to vote for a particular candidate, that the death or withdrawal of that candidate released them from any prior obligation, and that they were henceforth free agents, able to vote for any candidate they chose. The balance of opinion among constitutional scholars is that presidential electors are free agents, able to vote as they please, notwithstanding pledges or other commitments required by the state parties or state law to support the candidates of the party that nominated them. While the party national committees may thus appoint a replacement, they might not be able to guarantee that all electors would vote as instructed, particularly in the event of a closely contested election, or disputes over the national committee's choice of a replacement candidate or candidates. The historical record provides little guidance for this situation: only once in the nation's history has a presidential candidate died between the election and meeting of the electors. Horace Greeley, the 1872 presidential nominee of the Democratic and Liberal Republican Parties, died on November 29 of that year, 24 days after the election, but six days before the December 5 meeting of the electors. The Democratic National Committee did not meet to name a replacement candidate—63 Greeley electors voted for other candidates, while three voted for Greeley. When the joint session of Congress convened to count the electoral votes on February 12, 1873, the three Greeley votes were not recorded, "the said Horace Greeley having died before the votes were cast." Even so, the question as to the validity of Greeley's electoral votes was of little concern, since the "stalwart" or "regular" Republican nominee, Ulysses S. Grant, had won the election in a landslide, gaining 286 electoral votes. The second period during which succession procedures would be invoked in the event a President-elect or Vice President-elect were to die or leave the ticket occurs between the time the electors vote and Congress counts the electoral votes.