years until the Republican Revolution, broken only by brief Republican majorities. There was a significant change in U.S. politics in 1960, and this is seen by some as a transition to a sixth party system. Since the mid-1960s, despite a couple of landslides (such as Richard Nixon carrying 49 states and 61% of the popular vote over George McGovern in 1972; Ronald Reagan carrying 49 states and 58% of the popular vote over Walter Mondale in 1984), Presidential elections have been competitive between the predominant Republican and Democratic parties and no one party has been able to hold the Presidency for more than three consecutive terms. In the 2012 United States presidential election, only 4% separated the popular vote between Barack Obama (51%) and Mitt Romney (47%), although Obama won the electoral vote (332–206). Throughout every American party system, no third party has won a Presidential election or majorities in either house of Congress. Despite that, third parties and third party candidates have gained traction and support. In the election of 1912, Theodore Roosevelt won 27% of the popular vote and 88 electoral votes running as a Progressive. In the 1992 Presidential election, Ross Perot won 19% of the popular vote but no electoral votes running as an Independent. Modern American politics, in particular the electoral college system, has been described as duopolistic since the Republican and Democratic parties have dominated and framed policy debate as well as the public discourse on matters of national concern for about a century and a half. Third Parties have encountered various blocks in getting onto ballots at different levels of government as well as other electoral obstacles, such as denial of access to general election debates. Since 1987, the Commission on Presidential Debates, established by the Republican and Democratic parties themselves, supplanted debates run since 1920 by the League of Women Voters. The League withdrew its support in protest in 1988 over objections of alleged stagecraft such as rules for camera placement, filling the audience with supporters, approved moderators, predetermined question selection, room temperature and others. The Commission maintains its own rules for admittance and has only admitted a single third-party candidate to a televised debate, Ross Perot, in 1992. Some parts of the US have had their own party systems, distinct from the rest of the country. In Puerto Rico, there is a multi-party system with the Popular Democratic Party and New