He opened the panel by calling himself a "recovering candidate," encouraged activists to learn from his campaign's strategy and said only that he was "thinking about" whether he will take another plunge into electoral politics.

Democrat Jon Ossoff was given a hero's welcome at the Netroots Nation panel on Saturday, greeted by a dozen supporters wearing his campaign T-shirts who packed the first few rows of the room.

Ossoff lost the 6th District race in June to Republican Karen Handel by 4 points after the most expensive U.S. House election ever. He raised nearly $30 million and spent the bulk of the cash on TV ads that he said ground to a begrudging stalemate: "No one could back down, and it had diminishing effects."

Acknowledging he didn’t win the race - “take this with a grain of salt,” he said - Ossoff urged other would-be candidates to focus on building a grassroots army of volunteers to deliver on-the-ground intensity to match the battle on the airwaves.

And he said his campaign, which spurred visits by Donald Trump, Mike Pence and other GOP luminaries, proved that seats drawn to be “impenetrable” to Democratic challengers could be competitive.

“In the second round here, it was a full-on battle royale. You had a scenario comparable of what a competitive race will look like next cycle. And still the margin was tight,” said Ossoff. "And if you replay that scenario over and over again in the 60 or 70 districts more competitive than the Sixth, it bodes well - but it’s no reason to be over-confident.”

He shared the stage with David Nir, the Daily Kos political director who helped jumpstart his campaign by raising record sums for the first-time candidate.

“We’ll never see the likes of the fundraising we had for Jon’s campaign ever again,” said Nir, adding that it outpaced the cash it raised for liberal icon Sen. Elizabeth Warren.

Ossoff interjected, to laughter: “Appreciate it."

In hindsight, Ossoff said, he would have made some “technical changes” to his campaign. He would have sought more early-voting sites in the district, which stretches from east Cobb to north DeKalb. And he would have more aggressively pushed back on escalating “cynical” attacks from national GOP groups that sought to paint him as a naive, and sometimes dangerous, charlatan.

“We do have to fight back when folks resort to tearing apart society to win elections.”

Of the internal Democratic battles between progressive advocacies and establishment-types that are dividing the party, Ossoff insisted “Democrats are united no matter what you hear on cable news or the hot-take.”

"My message for folks who are wringing their hands is snap out of it and get back in the fight."

And to other prospective candidates either inspired or chastened by his experience, he had this counsel:

“My first piece of advice is run. And run fearlessly.”

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