Outside Atlanta on Friday, Jon Ossoff offered a decidedly un-Sanders-like vision of the future in Georgia’s Sixth Congressional District, a conservative-leaning patchwork of office plazas and upscale malls, where voters attended his campaign events wearing golf shirts and designer eyewear.

In a special election that has become the most expensive House race in history, Mr. Ossoff, a 30-year-old former congressional aide, presented himself as essentially anti-ideological. Greeting suburban parents near a playground and giving a pep talk to volunteers, he stressed broadly popular policies like fighting air and water pollution and preserving insurance coverage for people with pre-existing conditions.

Bucking the left, Mr. Ossoff said in an interview that he would not support raising income taxes, even for the wealthy, and opposed “any move” toward a single-payer health care system. Attacked by Republicans for his ties to national liberals, Mr. Ossoff said he had not yet given “an ounce of thought” to whether he would vote for Nancy Pelosi, the House Democratic leader, in a future ballot for speaker.

His own race, Mr. Ossoff told supporters, was about “sending a message to Washington.” But that message, he said, was about “decency and respect and unity, rather than division.”

“There’s a coalition of folks here in Georgia who want representation that’s focused on local economic development and on accountability,” Mr. Ossoff said in the interview, “and not on the partisan circus in Washington.”

The tension between Mr. Ossoff’s message and the appetites of the national Democratic base has not appeared to hinder his bid for Congress. He has raised more than $23 million, an astonishing sum, largely in small online donations from Democrats seeking to put a dent in the Republicans’ House majority. Several polls over the last week showed Mr. Ossoff leading his Republican opponent, Karen Handel, though both parties agree that the race remains a tossup.