Legal career In 1906, Pedro was admitted to the bar. From 1907 to 1909, he served as
justice of the peace and as provincial fiscal in San Fernando, Pampanga. As provincial fiscal, he was also Pampanga's prosecuting attorney. He served as councilor of San Fernando from January 1910 to March 1912. From 1916 to 1922, he represented the Second District of Pampanga in the
House of Representatives of the Philippine Islands for two terms. Abad Santos joined the
Nacionalista Party on October 3, 1916. In his term in the House of Representatives, Abad Santos supported
Manuel Quezon in a 1917 bill providing equal rights to divorce on the grounds of adultery for both sexes and a 1919 bill granting women's suffrage. He began offering
pro bono legal services when he was a municipal councilor. Around a third of his cases were composed of peasants and workers, who were subsidized by the rest of his clients, who were from prominent families. His law office was a
nipa hut near the Abad Santos ancestral house. He founded a private law firm with sibling Jose Abad Santos from 1920 to 1921 in Calle Azcarraga (now
Recto Avenue) in Manila. The firm had the
Manila Railroad Company as one of its clients. He was also included among the 28 members of the second Philippine Independence Mission to the United States in 1922, headed by
Sergio Osmeña. After his return from the United States, he withdrew from insular-level politics and returned to San Fernando to offer legal services to peasants against landlords. In 1927, Pedro lost the election for
governor of Pampanga to
Sotero Baluyut. Pedro ran for governor of Pampanga in 1934, 1937, and 1940 afterward, all losing to Baluyut. Abad Santos joined the
Popular Front in 1937. As such, he represented the Popular Front in the 1937 and 1940 elections. His votes increased from around 6,000 to 1934 to 16,000 the following election, and he lost by a margin of around 5,000 to 6,000 votes in 1940. Abad Santos's political alliance with Quezon ceased with their conflict on the
Hare–Hawes–Cutting Act, which Quezon strongly disapproved. Abad Santos supported the passing of the bill as he argued that the act's provisions could be negotiated during the ten-year Commonwealth period. During one of the debates, Quezon accused Abad Santos and Honorio Ventura,
Secretary of Interior and political ally of Abad Santos, of cheating in elections.
Socialist Party of the Philippines After his loss in the 1927 gubernatorial election, Abad Santos joined his friends
Crisanto Evangelista, Antonio de Ora and Cirilo Bognot to study at the
Lenin Institute in
Moscow, in then
Soviet Union. In 1929, Abad Santos founded the
Aguman ding Maldang Talapagobra (AMT), a worker's union. When the
Partido Komunista ng Pilipinas (PKP) was outlawed by the Supreme Court, Pedro founded the
Socialist Party of the Philippines in 1932. The base of membership of the Socialist Party of the Philippines sprung from the AMT. One of the men recruited was
Luis Taruc, who became a
cadre of the Socialist Party. On November 7, 1938, during the 21st anniversary of the Russian
Bolshevik Revolution, the PKP and the Socialist Party of the Philippines held a convention at the
Manila Grand Opera House where they agreed to merge their organizations to form the Communist Party of the Philippines. Crisanto Evangelista was elected the organizations' president, Pedro Abad Santos its vice president, and
Guillermo Capadocia its secretary general. Pedro's protégé, Luis Taruc, described Pedro as a
Marxist but not a
Bolshevik. Abad Santos considered all members of the AMT as party members, and believed that the Philippines should remain its economic, political, and cultural ties with the United States with a more equitable share of wealth among classes.
Preparations for World War II The Communist Party of the Philippines merger recognized the imminence of a war in Asia with Japan's expansionism, and the party discussed on its stance on independence to avoid affiliation with the United States. Abad Santos admitted to colleague
Sol Auerbach that he was not sure of what to do, and wanted to "consult fellow workers first". By 1940, he was receiving reports from party members and his union of Japanese espionage. As such, he advised every town to prepare for warfare. In June 1941, Abad Santos sent Laurence E. Salisbury, the
US Foreign Service officer assigned to Sayre, a memorandum claiming that "Quezon and his men are secretly negotiating with agents of Axis governments" for their "business connections [...] with Fascists, Falangists, Japanese" and suggested that the US withdraw its patronage to Quezon and install a Popular Front government. Salisbury acknowledged the suggestion and his arguments, but noted that the offer would be impossible. In a following interview, Abad Santos requested Salisbury a channel where their positions and views would reach US officials. On July 17, Abad Santos and Evangelista called upon Sayre to express the coalition's support to the United States, and wished for "the moral support of the American authorities" when Sayre asked them any request to make of US officials. Sayre replied that he could not interfere with Commonwealth government, but acknowledged the loyalty of the party to the US. After the bombing of Pearl Harbor, the PKP committee conducted an emergency meeting in Manila from December 8 to 11, which resulted in a memorandum published in newspapers and presented to Quezon and US high commissioner
Francis Sayre. The memorandum called for an anti-Japanese united front, a communal contribution to the war effort, and pledged loyalty to democracy and to the Philippines and the US governments. == Peasant uprising ==