In 1892, Glavinov became acquainted with Dimitar Blagoev's exposition of the Marxist view of history and in 1894 he entered the new Bulgarian Social Democratic Workers Party.

In the same year, under Vasil Glavinov's leadership and in order of Blagoev, the first Social-Democratic group in Ottoman Macedonia was formed in Veles.

[7] In 1896, Glavinov founded a Macedonian-Adrianople Social Democratic Group, as part of the Bulgarian Workers' Social-Democrat Party.

This "federative Macedonian republic," (some kind of Switzerland on the Balkans), would be with a cantonal organization, with separate territorial units for all the "national elements" living there.

After the Young Turk Revolution in 1908, he moved back to the Ottoman Empire and initially gravitated around the People's Federative Party (Bulgarian Section).

In the same year he participated also in the First Balkan Socialist Conference held in Belgrade, which important aspect was the call for a solution to the Macedonian Question.

As a consequence, on the eve of the Balkan Wars in 1911 Glavinov moved back to Sofia, where he joined the Bulgarian Social Democratic Workers' Party (Narrow Socialists).