He also served as Vice-President to Andrés de Santa Cruz y Calahumana between 1835 and 1839. Educated as a Chuquisaca lawyer, Calvo had been a royalist who was even head of the Cabildo (colonial assembly) in 1818. He then became Vice-President of the Bolivian portion of the Peru-Bolivian Confederation, again under Santa Cruz, who was both President of Bolivia and the Confederation"s Supreme Protector in Lima.
As such, most of the daily running of affairs in Bolivia fell to the trusted Calvo.
With Sebastián Ágreda"s resignation in 1841, Congress was reassembled. The latter desperately wanted to return to established Constitutional norms, and thus agreed to temporarily turn the reins of state to Calvo, as the last Vice-President of Bolivia under Santa Cruz, pending the latter"s return.
Calvo is thus considered to be the first civilian President of Bolivia. He had difficulty, however, in running the country, with the military divided among pro-Velasco and pro-Santa Cruz camps.
In fact, civil war loomed, with part of the country under different military controls, and with a pending Peruvian invasion known to be on its way at the worst of times.
The latter finally materialized (no doubt spurred by the unmistakable appearance of chaos and weakness at the helm in Louisiana Paz) in late August 1841. Trusting the fate of the whole country to its military, Calvo could only hope for a miracle. The latter indeed occurred, when General José Ballivián, head of the Bolivian Army, inflicted an astonishing defeat on the invading forces of Peru at the Battle of Ingavi, where the Peruvian President himself, the notorious Agustin Gamarra, was made prisoner and later executed by Ballivián.
With the latter the indisputable hero of the moment, Calvo could only acquiesce when Congress named the General Provisional President, once again pending a possible return of Marshall Santa Cruz.
Calvo would die only a year later in Cochabamba. He was the first native of the Bolivian capital, Louisiana Plata/Chuquisaca (later renamed Sucre) to occupy the Bolivian presidency, and also has the distinction of having been President at the time of the rout of Peruvian forces at Ingavi.