In 2009, Ríos Piter was elected to the Chamber of Deputies for the LXI Legislature; his district was the only win for the PRD in Guerrero that year. He was one of the PRD's leaders in the chamber that legislature, being the head of the PRD caucus in the Chamber of Deputies and also presiding over the Political Coordination Board and the Finance and Public Credit Commission. His commission assignments reflected his educational and government background, ranging from Ranching to Budget Analysis. With his three-year term up, the PRD successfully ran Ríos Piter for the Senate, for a six-year term to cover the LXII and LXIII Legislatures in 2012. He sat on six regular committees, being secretary on four of them, in the LXII Legislature, and in the LXIII Legislature, he presided over the Population and Development Commission while sitting on others related to public finances, corruption, and radio, television and film, among others. During his tenure, he mounted a bid to be the PRD gubernatorial candidate in 2015 in Guerrero, but he declined over his outrage that Jesús Ortega Martínez, part of another faction of the PRD known as "Los Chuchos", obligated him to sign a political pact with disgraced governor Ángel Aguirre Rivero to be the candidate. The Senate also named Ríos Piter as one of its designees to the Constituent Assembly of Mexico City, but his nomination failed to receive enough votes in the Senate. In September 2016, Ríos Piter proposed legislation that would protect Mexicans should Donald Trump, as US president, inflict punishment on the country in order to fund the proposed border wall. He stressed that the economic welfare of the United States and Mexico was at stake. "At a time like this, it's vital for us to understand why this relationship benefits both. We're neighbors, we're friends, we're partners," he said. "He's putting at risk."
Departure from the PRD and independent presidential candidacy
On 14 February 2017, Ríos Piter announced he would leave the PRD in order to start a nonpartisan movement called the Movimiento Jaguar. His departure brought to eight the number of defections from the PRD among the senators it had elected in 2012. In leaving the PRD, he declared his resignation not just from the party but from "an entire system that now only produces noise and confrontation". Three months later, he announced his intention to run for president in 2018 as an independent candidate. By early February 2018, he had reached the signature requirement—one percent of the electoral rolls in at least 17 of Mexico's 32 states—to appear on the 2018 presidential ballot as an independent, becoming the second candidate to do so behind Jaime Rodríguez Calderón. However, Ríos Piter did not reach the required number of signatures to appear on the ballot. Ríos Piter also made calls to clear the political field, including Calderón and Margarita Zavala, and join forces to create a unified independent presidential campaign. According to Ríos Piter, the goal of such a combined candidacy would be to create a common platform "to confront the political parties and their candidates, who must be sent to rehabilitation".