two parties have won every U.S. presidential election since 1852 and have controlled the U.S.Congress since at least 1856. From time to time, a third party has achieved some minor representation at the national and state levels. Since the Great Depression and the New Deal, and increasingly since the 1960s, Democratic Party has generally positioned itself as center-left in American politics, while the Republican Party has generally positioned itself as center-right, although there are other factions within each. Organization of American political parties Unlike in many other countries, the major political parties in America have no strong central organization that determines party positions and policies, rewards loyal members and officials or expels rebels. A party committee or convention may endorse a candidate for office, but the determination of who will be the party's candidate in the general election is usually done in primaries open to voters who register as Democrats or Republicans. Furthermore, elected officials who fail to "toe the party line" because of constituent opposition to it, and "cross the aisle" to vote with the opposition, have (relatively) little to fear from their party. Parties have state or federal committees that act as hubs for fundraising and campaigning, (See, Democratic National Committee, Republican National Committee) and separate campaign committees which work to elect candidates at a specific level, but do not direct candidates or their campaigns. In presidential elections, the party's candidate serves as the de facto party leader, whose popularity helps or hinders candidates further down the ballot. Midterm election are usually regarded as a referendum on the sitting president's performance. Some (Lee Drutman, Daniel J. Hopkins writing before 2018) argue that in the 21st century, along with becoming overly partisan, America politics has become overly focused on national issues and "nationalized", so that even local offices, formerly dealing with local issues now often mention the presidential election. The two-party system in the U.S. "Third" political parties have appeared from time to time in American history but seldom lasted more than a decade. They have sometimes been the vehicle of an individual (Theodore Roosevelt's "Bull Moose" party, Ross Perot's Reform Party); had considerable strength in particular regions (Socialist Party, the Farmer-Labor Party, Wisconsin Progressive Party, Conservative Party of New York State, and the Populist Party); or continued to run candidates for office to publicize some issue despite seldom winning even local elections (Libertarian Party, Natural Law Party, Peace