"I wanted to meet face-to-face with my followers," Boudou said as he opened the event in the San Telmo quarter of the Argentine capital.
About 500 of his 64,000 Twitter followers signed up through the microblogging site. They were invited to post their questions on the site.
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"Twitter helps improve the quality of democracy. We can communicate without having the media in the middle," Boudou said.
The evening was also an occasion for Boudou, vying to be the ruling party's candidate for mayor of Buenos Aires, to highlight the themes of his campaign before the July 10 vote.
About 500 followers were chosen to attend the event but "1,700 people signed up and more than 3,000 questions were posed" on Twitter, said Mariano Feuer, one of the organizers.
In an hour of debate, #boudou20 became the most popular hashtag on the social network in Argentina.
