BUENOS AIRES — With his fusty corduroy blazer, diffident mien and unpolished website, Andy Tow, an anonymous civil servant with a flair for data crunching, is emerging as an unlikely rock star of Argentina’s election season.

Mr. Tow, 45, spends his days assisting a congressman, often performing mundane tasks like answering phones or booking flights. But in the evenings, he morphs into a prodigious statistician who tells the complicated stories of domestic politics by turning raw data into online graphics. This rare pursuit has been winning Mr. Tow influence — and some ire — among scholars, pundits and, now, even voters.

“It’s an addiction; I do it all for artistic love,” he said over lunch at a coffee shop opposite the congressional palace here. “It used to be more underground. I never gave it much publicity. I’m just mad about computing and numbers.”

As Argentines muse on a tight race for the presidency before they go to the polls for a runoff election on Sunday, Mr. Tow’s passions and, more recently, his Twitter account are catapulting him beyond his usual niche audience to a wider public.