In the early 1890s he converted from Narodnism to Marxism and joined the secret Social-Democratic circles of Peter Struve and Julius Martov.

In 1896 Potresov helped found the St. Petersburg Union of Struggle for the Emancipation of the Working Class, one of the nuclei of the Russian Social-Democratic Workers' Party (RSDRP).

After his release in 1900 he left Russia and lived mostly in Germany, where he had good contacts among the German Social-Democrats and among the Russian exiles.

Together with Plekhanov, Akselrod, Zasulich, Lenin and Martov, Potresov launched the journal Iskra (The Spark), whose mission it was to defend orthodox Marxism (as Plekhanov understood it) against the various heresies of Economism and Revisionism that were then current among Russian Social-Democrats.

In 1898 Potresov helped found the Russian Social-Democratic Workers' Party (RSDRP).

Lenin proposed to reduce the editorial board to himself, Plekhanov and Martov, discarding the less productive Akselrod, Zasulich and Potresov.

The Revolution of 1905 brought Potresov back to Russia, where he edited the Menshevik papers Nachalo (Beginning) and Nevskii Golos (New Voice).

Nevertheless, Liquidationism was a strong current among Mensheviks, and Potresov, as editor of the Liquidationist journal Nacha Zariia (Our Charge), was one of its most prominent theoreticians.

Potresov sought to assist the war effort by joining the Moscow Military Industrial Committee.

During preparations for the elections to the Constituent Assembly, Potresov threatened to withdraw from the RSDRP and head a separate list.

In 1918 he withdrew from the RSDRP and joined the Union for the Salvation of Russia, a group uniting right-wing Mensheviks, SRs, and Popular Socialists.