The Raza Unida Party was established on January 17, 1970, at a meeting of 300 Mexican Americans at Campestre Hall in Crystal City, Texas. José Ángel Gutiérrez and Mario Compean, who had helped found MAYO (the Mexican American Youth Organization) in 1967, were two of its principal organizers. In December 1969, at the first and only national MAYO meeting, Chicano activists had endorsed the formation of a third party, an idea that Gutiérrez had proposed in establishing MAYO. After RUP filed for party status in Zavala, La Salle, and Dimmit counties in January 1970, it began its eight-year quest to bring greater economic, social, and political self-determination to Mexican Americans in the state, especially in South Texas, where they held little or no power in many local or county jurisdictions although they were often in the majority. Membership in the party was open to anyone who was committed to RUP's goals. The party fielded candidates for nonpartisan city council and school board races the following April in Crystal City, Cotulla, and Carrizo Springs and won a total of fifteen seats, including two city council majorities, two school board majorities, and two mayoralties. In October 1971, RUP held its state convention in San Antonio and voted to organize at the state level over the objections of Gutiérrez, who believed that the party should strengthen its rural standing rather than expend its energy on a state party. Compean rallied enough support for a state organization on the grounds that it would give a boost to the Chicano movement in Texas and repeat the success it had attained in Crystal City throughout Texas.
With the state party apparatus in place, RUP sought a candidate for the 1972 gubernatorial election, first calling upon such well-known Democrats as state senator Carlos Truán, Hector García (founder of the American G.I. Forum), and state senator Joe Bernal. All refused to run for the position. The party finally found a candidate in Ramsey Muñiz, a lawyer and administrator with the Waco Model Cities Program. Alma Canales of Edinburg, who had been a farmworker and journalism student at Pan American University, became the RUP candidate for lieutenant governor, although at twenty-four she was too young to take the office constitutionally. Her presence on the RUP slate was considered a sign that women had a crucial role in the party. Although they seemed an unusual match, the two resembled many of the RUP rank and file, who were young and university educated. Like others in the party, they had also been members of MAYO. Besides Muñiz and Canales, RUP ran candidates for nine other state offices, including member of the Railroad Commission, state treasurer, and member of the State Board of Education. RUP candidates also ran for local posts in Hidalgo, Starr, Victoria, McLennan, and other counties.
The party, which had spread to many other states, held its first national conference in El Paso on September 1–4, 1972. About half of the estimated 1,500 participants were women, and a large number of elderly people also attended. The delegates formed the Congreso de Aztlán to run the national party and elected Gutiérrez as RUP national chairman. Despite his standing as the party's chief political candidate, Muñiz was not much heeded. As a result, he left the gathering early to campaign in the governor's race. The RUP platform that Muñiz put before voters, while emphasizing Mexican-American community control, bilingual education, and women's and workers' rights, bore similarity to the values espoused by the liberal faction of the state Democratic party, which supported Frances (Sissy) Farenthold for the party's gubernatorial nomination. In spite of this, Muñiz did not receive strong support from liberals. Ultimately, even Farenthold endorsed Dolph Briscoe, to whom she had lost the nomination, although she had once referred to him as "a bowl of pablum." Muñiz won 6 percent (214,149) of the votes in the November election, thus reducing Briscoe's margin of victory so that the race was the first in the twentieth century in which a Texas governor was elected with less than a majority. Muñiz won heavily in some South Texas counties and had a decent turnout in large cities. Over the next two years RUP solidified its South Texas rural base and racked up more nonpartisan victories in the Winter Garden Region. It also achieved political successes in Kyle and Lockhart. Its urban support, though quite strong among university activists and barrio youth and politicians, remained small. This ultimately hurt the party's future, since many Hispanics lived in the state's major urban areas and their support of RUP was necessary for the party to have a larger political impact.
In 1974, RUP was ready for another try at the governor's race, with Muñiz once again its candidate. The party also ran a slate of fourteen men and two women for state representative from Lubbock, Houston, San Antonio, Austin, Falfurrias, Crystal City, and other cities. As in the 1972 election, the RUP campaign literature emphasized the party's Chicano foundation; but it also asserted a desire to "ensure democracy for [the] many, not the few" and the need to preserve "human and natural resources." In addition, it called for the prosecution of industrial polluters. In his announcement for the governor's race on January 16, 1974, Muñiz sought to maximize the party's appeal to a broader spectrum of the state's voters, stressing RUP's ideas for new modes of transportation, improved funding of public education, better medical care, and solutions to urban problems. But RUP did not fare well in the 1974 general election. Muñiz got only 190,000 votes and posed no real threat to Briscoe's reelection. In addition, none of the sixteen candidates for the state House garnered enough support to win. The party's sole real victories were in Crystal City, where cofounder Gutiérrez was elected as Zavala county judge and the party successfully defended its dominance of other county offices. Nonetheless, by its numerous victories in South Texas, RUP had achieved Mexican-American political dominance in some cities and altered the state's political life. Several Mexican-American women were significant participants at the state and national level. Evey Chapa, for instance, ensured that RUP's state executive committee provide for a female member; Virginia Múzquiz headed the RUP nationally from 1972 to 1974; and María Elena Martínez served as the last head of the party in Texas from 1976 to 1978. Likewise, Evey Chapa, Ino Alvárez, and Martha Cotera have been credited with organizing Mujeres Por La Raza, the women's caucus within RUP.
In the four years after the 1974 election, RUP's fortunes diminished, with activism slowing except in some enclaves in South Texas. Even in Crystal City, its bedrock, RUP lost control in 1977. The party also suffered losses in its membership, and some of its original leaders, including Willie Velásquez , allied themselves with new political initiatives, such as the Mexican American Democrats. Perhaps two of the biggest blows to party morale were the arrests in July and November 1976 of former RUP gubernatorial candidate Ramsey Muñiz on drug charges. He pled guilty to one count and was sentenced to fifteen years. The party was considerably weakened as it entered the final and fatal 1978 election, when RUP gubernatorial candidate Mario Compean won only 15,000 votes. At the election-day fiasco in 1978, RUP lost state funds for its primary and was effectively eliminated as a party. Some historians have stated that RUP, with its various successes and failures, came at the right moment in Mexican-American history in the state. Writing in 1978 in The Tejano Yearbook: 1519–1978, Philip Ortega y Gasca and Arnoldo De León noted that the establishment of RUP in the 1930s would have been "premature" because violence was still a common response to Texas Mexicans' political ambitions. Nevertheless, the authors also argue that RUP was neither a new phenomenon nor a "radical" one but a continuation of Tejano political initiatives. Nineteenth-century Tejanos had formed various movements, such as Botas and Guaraches and special benevolent associations, to defend their interests. RUP was intended to do the same for Mexican Americans in the 1970s.