The Tellería family was of Carlist political sympathies; Agustín's father served as officer in the legitimist ranks during the Third Carlist War, and also following defeat he remained a “modelo de perseverancia en el defensa de un ideal”.
Agustín inherited the Traditionalist outlook.
Together with the entire family in 1905 he co-signed a homage message, directed to the Pope Pius X and protesting alleged masonic manipulations in France.
In the mid-1900s he engaged in the Carlist youth organisation and over time grew to president of the Tolosa branch of Juventud Carlista; it is not clear why he was not active in his native Vergara arm of the structures.
In 1908 he was already mingling with party executives in Gipuzkoa, e.g. he entered the committee headed by the provincial jefé Tirso de Olazabal and entrusted with organizing a grand regional Traditionalist rally in Zumarraga.
Also in the early 1910s Tellería was noted in the press for various protests in defense of religion and aimed against perceived blasphemous initiatives and incidents.

In the late 1910s Tellería was not recorded either in Traditionalist or religious organizations, and studies on Carlism of the era do not mention his name.
At that time the movement was increasingly fragmented due to a conflict between the key theorist, Juan Vázquez de Mella, and the claimant Don Jaime.
Most of the Gipuzkoan party leaders tended to side with the former, who advocated a grand ultra-right alliance with dynastic threads played down; Tellería followed the same path.
When the crisis erupted during a showdown of early 1919, he joined the rebels – to be known as Mellistas – and broke away.
In late 1919 he agreed to represent the emerging new grouping in the race to the Cortes, and was officially reported as standing in the election campaign from the district of San Sebastián.
It is not clear whether he eventually withdrew or was defeated, as none of the press titles of the era provided details on the number of votes he could have gathered.

In the early 1920s the Mellistas tried to build their own organisation, but the process went on slowly with many defections along the way.
Tellería was not among the disillusioned.
As late as in mid-1923 he was touring Gipuzkoa and spoke at party rallies.
He counted among most-recognized provincial party leaders, along Víctor Pradera, Marcelino Oreja and Antonio Pagoaga.
Nonetheless, the Primo de Rivera coup brought political life in Spain to the standstill.
It seems that Tellería’s party activity ceased; if referred in the press in the mid- and late 1920s, it is only on social columns or in sporting sections, noted as sponsor of rowing teams.
He might have been involved in running the family tanning company, especially that his father was already a septuagenarian.
However, it is more likely that he engaged in pharmaceutical business, as he was soon to be known as “farmacéutico”; this reference is invoked also in present-day historiographic scientific works, yet it is not clear what it exactly stands for.
The Tellería family was of Carlist political sympathies; Agustín's father served as officer in the legitimist ranks during the Third Carlist War, and also following defeat he remained a “modelo de perseverancia en el defensa de un ideal”. Agustín inherited the Traditionalist outlook. Together with the entire family in 1905 he co-signed a homage message, directed to the Pope Pius X and protesting alleged masonic manipulations in France. In the mid-1900s he engaged in the Carlist youth organisation and over time grew to president of the Tolosa branch of Juventud Carlista; it is not clear why he was not active in his native Vergara arm of the structures. In 1908 he was already mingling with party executives in Gipuzkoa, e.g. he entered the committee headed by the provincial jefé Tirso de Olazabal and entrusted with organizing a grand regional Traditionalist rally in Zumarraga. Also in the early 1910s Tellería was noted in the press for various protests in defense of religion and aimed against perceived blasphemous initiatives and incidents.
In the late 1910s Tellería was not recorded either in Traditionalist or religious organizations, and studies on Carlism of the era do not mention his name. At that time the movement was increasingly fragmented due to a conflict between the key theorist, Juan Vázquez de Mella, and the claimant Don Jaime. Most of the Gipuzkoan party leaders tended to side with the former, who advocated a grand ultra-right alliance with dynastic threads played down; Tellería followed the same path. When the crisis erupted during a showdown of early 1919, he joined the rebels – to be known as Mellistas – and broke away. In late 1919 he agreed to represent the emerging new grouping in the race to the Cortes, and was officially reported as standing in the election campaign from the district of San Sebastián. It is not clear whether he eventually withdrew or was defeated, as none of the press titles of the era provided details on the number of votes he could have gathered.
In the early 1920s the Mellistas tried to build their own organisation, but the process went on slowly with many defections along the way. Tellería was not among the disillusioned. As late as in mid-1923 he was touring Gipuzkoa and spoke at party rallies. He counted among most-recognized provincial party leaders, along Víctor Pradera, Marcelino Oreja and Antonio Pagoaga. Nonetheless, the Primo de Rivera coup brought political life in Spain to the standstill. It seems that Tellería’s party activity ceased; if referred in the press in the mid- and late 1920s, it is only on social columns or in sporting sections, noted as sponsor of rowing teams. He might have been involved in running the family tanning company, especially that his father was already a septuagenarian. However, it is more likely that he engaged in pharmaceutical business, as he was soon to be known as “farmacéutico”; this reference is invoked also in present-day historiographic scientific works, yet it is not clear what it exactly stands for.
Agustín Tellería Mendizábal