At the time of his birth in 1856, the town of Vršac was part of the Voivodeship of Serbia and Banat of Temeschwar crown land in the post-1849 Habsburg monarchy.

Thereafter, Tomić was involved in Serb politics in Habsburg-controlled parts of present-day Serbia (Serbian Vojvodina).

[3][4] In 1889, following a series of articles regarding nature of his employment at Zastava, in which he implicated his wife Milica Miletić, Tomić stabbed to death a liberal political rival, Miša Dimitrijević, the editor of Branik magazine, in Novi Sad.

Dimitrijević alleged that Milica, who was the daughter of famed lawyer and Novi Sad mayor, Svetozar Miletić, who in turn was the founder of Zastava, arranged the position of editor for Tomić as a part of a dowry and mentioned in a daily journal that he was in a possession of a letter that demonstrated this intention and sent the letter in question to Jaša in written correspondence.

In 1919 Jaša Tomić, still, the leader of the Radicals in Vojvodina Province, whose failing health prevented him from taking a more active role was perfectly straightforward in stating to Croat politicians (including Vjekoslav Spinčić) that "we are not one" in nationality[citation needed].