[3] Rivero first entered the political field as a member of the Revolutionary Nationalist Movement (MNR), a party with a long-standing dominant presence in the Beni Department since the country's transition to democracy.

[5] Nonetheless, he remained mistrusted among many sectors of Beni society, resulting in ongoing conflicts with the department's trade unions and indigenous rights groups for the duration of his term.

The deadline for this ultimatum expired on 1 June, leading organized labor and indigenous groups to institute a blockade along the highway near Puente San Pablo, connecting Trinidad to Santa Cruz de la Sierra.

The ensuing conflict between law enforcement and protesters made its way from the highway into the town, leaving dozens wounded as soldiers and police shot bursts of automatic weapons and raided homes.

[14][15] In his presidential memoir, Mesa shifted blame away from the former prefect, lamenting that "the sad episode in San Carlos [sic] unjustly ousted Erwin Rivero, who had done a good job until then".

Many of Rivero's supporters deflected blame for the violence in San Pablo onto Moisés Shriqui, the mayor of Trinidad, whom they accused of orchestrating the incident to discredit the prefect's administration.

In these regions, the party turned to figures who had not historically belonged to the organization, who held experience in fronts the MAS otherwise harshly criticized, and who came from sectors even opposed to its socialist agenda.

[19] Rivero campaigned for the MAS in the 2009 general elections, for which he sought to become the party's gubernatorial candidate the following year,[α] arguing that his support had made inroads for the government among Beni's middle class.

In a surprise move, President Evo Morales personally selected Jordan as his party's candidate, sidelining Rivero, whose political past "weighed heavily" on the final decision.