Sen. Mark R. Warner (D-Va.) is concerned about health and retirement benefits for workers. (Andrew Harrer/Bloomberg)

Sen. Mark R. Warner sighed and stopped to confront two aides staring at their phones and leading him in circles around downtown Philadelphia. On Day 2 of the Democratic National Convention, humidity topped 90 percent and the senior senator from Virginia was late again.

“Are we going this way? Do you guys know?” he said, a suit jacket slung over his sweaty shoulder.

At the moment Virginia’s other senator, Tim Kaine, was preparing to accept the Democratic nomination for vice president, Warner was, well, lost.

As Kaine and Virginia Gov. Terry McAuliffe (D), a close friend of Hillary Clinton, basked in the national spotlight during the convention, Warner opted to forge a quieter path away from the 2016 political circus.

The restless 61-year-old senator has focused his energy on a problem he thinks is threatening the quality of life for millions of Americans: the lack of health and retirement benefits for workers in the economy of the 21st century. The solution, he said, requires nothing less than remaking the U.S. economy.

“I don’t think modern American capitalism is working for enough people,” Warner said at an event during the convention organized by the centrist Democratic think tank Third Way. “I think we see that in the anger in our party. I think we see it in some of the frustration on the Republican side.”

The notion that a worker would stay at one company and accrue benefits over a lifetime is an anachronism, according to Warner.

People today switch jobs frequently and, in the gig economy characterized by Uber, increasingly eke out a living using freelance and part-time work. One in 3 workers are independent contractors. But that often leaves them without health care, disability insurance or pension benefits. Unprepared for retirement, let alone an injury or other unexpected expense, more workers than ever are vulnerable in a way that a social safety net tied to work cannot bear, he said.

Warner wants to re-engineer the American economy in a way that provides such a net for freelancers and contractors. He said he has not settled on exactly how portable benefits would work but in one scenario, freelancers and contractors would partially fund their own benefits and then carry them from job to job, with employers contributing as well.

A third party would handle a worker’s portable benefits package, Warner said. He is still trying to figure out the mechanics and is uncertain whether that function would fall to a private, for-profit company, a traditional labor union or another entity.

Some companies are already moving to offer a version of traditional benefits for part-time workers or independent contractors to help attract and retain employees.

Uber in May agreed to create a guild that could negotiate discounts on life insurance and disability benefits as well as provide education to about 35,000 New York drivers. Last week, online craft marketplace Etsy issued a report proposing changes to regulations that would allow sellers to put aside money to pay taxes, and create a federal government-run portal that would be in charge of certain benefits. And Handy.com, a home-cleaning platform, is pushing legislation in New York that could help its workers access benefits and training.

Warner finds the issue of portable benefits compelling because it combines several of his interests: the economy, technology and bipartisanship. It also gives him an excuse to travel the country talking about something that intrigues him more than the noisy presidential race.

In a recent speech to 100 employees at Fishbowl, an ­Alexandria-based restaurant-analytics company, Warner portrayed himself as a truth-teller with practical goals including creating more robust training courses in regions abandoned by manufacturing.

“The rest of the world’s not stopping because we have congressional gridlock or we have a presidential election,” he told the crowd.

As Republicans and Democrats talk about how the economy is failing the middle class, Warner said he wants to come up with fixes before the parties stake out hard positions favoring or opposing his ideas.

In November, he said he expects Clinton to win the White House, Democrats to take control of the Senate and Republicans to keep the House, allowing all the same partisan debates to play out as usual.

“If we don’t change the narrative, what’s really going to change?” he said.

A decade ago, Warner flirted with leveraging a successful governorship into a presidential bid, but ran for the Senate instead. He won in a landslide, capturing 65 percent of the vote and the majority in all but six of the commonwealth’s 133 cities and counties.

Six years later, he came close to losing to GOP strategist Ed Gillespie with a strategy that political experts said ignored sweeping demographic changes in the state. No longer were there enough Democrats or moderate Republicans in the Southwest to make Warner, a middle-of-the-road Democrat, unstoppable in every region. In the last several statewide elections, Democrats in Virginia won by wooing liberals in Northern Virginia and other urban centers.

The 2014 election cost Democrats their majority in the U.S. Senate but Warner saw it as a chance to work with the other side and promised to only file major legislation if a Republican co-sponsors it.

Warner — and Kaine — were among the 13 Senate Democrats who voted with Republicans to give President Obama power to swiftly implement the Trans- ­Pacific Partnership. In the current presidential race, the trade deal has become synonymous with shortchanging workers. Clinton turned against the TPP amid pressure from the left wing of her party, followed by Kaine shortly after he joined the national ticket.

Warner defended his position to three Bernie Sanders supporters who sought him out at a muggy beer garden fundraiser at the Democratic convention. He huddled with them and explained why the “social contract created in the ’30s and ’40s” does little to protect today’s workers.

“That is right in line with Bernie Sanders’s message that we’ve gotten behind,” said Alexander Hulvey, a 25-year-old Harrisonburg resident who works at a co-op grocery store. “And to hear a centrist senator from my state say that changed my opinion of him.”

In addition to impromptu pitches, Warner has held forth on the topic in dozens of speeches, panel discussions and round­tables.

It is unclear whether Warner’s message is breaking through the cacophony of the election year. But he persuaded the Aspen Institute to create the Future of Work initiative to study portable benefits. Warner is leading that effort, along with a Republican — Purdue University President and former Indiana governor Mitch Daniels.

“Let’s not surrender to the idea that we’re permanently paralyzed,” Daniels said in an interview. “If new things are going to happen, it will be people exactly like Senator Warner who can bring people together who could pull it off.”

Quentin Kidd, a political scientist and pollster at Christopher Newport University, said Warner’s decision to take on something as audacious as remaking capitalism makes sense.

“This may allow him to carve out his own space,” he said. “This may give people another way to talk about Mark Warner other than the senior senator who didn’t get picked.”