Upon his return to Bolivia, he entered political life as a supporter of José María de Achá, but when he Melgarejo ousted him, Campero was exiled to Chile and Argentina.

[5] Campero participated in the tragic events of 26 March 1865, when a rebellion led by former president Manuel Isidoro Belzu, with the support of the popular masses of La Paz, expelled Melgarejo from the city.

Belzu proclaimed himself head of state, however, Melgarejo, aware of his imminent defeat, entered the city making his way through the crowd and asked to have meeting with the populist caudillo.

The outbreak of the war with Chile in 1879 motivated him to offer his services to President Hilarión Daza, who ordered him to raise a military division with recruits from the southern departments of Bolivia, mainly Tarija and Potosí.

[12] The only relevant military action this division saw was the Battle of Tambillo, where Bolivian soldiers defeated a Chilean advance guard, an opportunity that was exploited by Campero, who could have retaken Calama.

[5] Campero assumed the provisional presidency at the request of a Board of Notables meeting in La Paz after the overthrow of Hilarión Daza in December 1879.

[13] The beginning of his government coincided with the virtual dismemberment of the Bolivian forces that were fighting alongside the Peruvians in the War of the Pacific, which motivated Campero to call for a new mobilization effort and personally assume the leadership of the allied troops.

The Campero government faced serious difficulties as a result of the war such as the abrupt interruption of foreign trade and the epidemics and famines ravaging the population, aggravated by the military demobilization.

[6] In his institutional performance, Campero promulgated a new constitution that inaugurated the cycle of the "oligarchic republic", under the influence of the liberal ideas professed by the new mining elite.

A proponent of rearmament and reinsertion into the war against Chile with an eye to recovering the lost territories, Campero was opposed in this endeavor by his vice-president, the Conservative Arce.

Arce was linked to Chilean monetary and financial interests and favored an "accommodation" with Santiago, essentially advocating the surrender of the Litoral in exchange for investment and perhaps a promise to obtain a port through previously Peruvian but now Chilean-occupied at Arica.

The status quo he helped create would last until the 1930s, although within the framework of a plutocratic and severely restricted version of democracy, in which only white or mestizo propertied elites could vote.