Heather Costello was strap-hanging in a subway car barreling toward the Democratic National Convention on Tuesday - unaware she was also barreling into a verbal brawl.

The Arizona emergency-room doctor was in Philadelphia with a backpack, reawakened ideals, and a T-shirt that proclaimed: THE REVOLUTION.

Costello, 46, had come for Bernie Sanders. She had come to be part of an antiestablishment uprising she had never seen in a life of watching middle-class wages and liberal policies disappear.

"People hadn't been paying attention," Costello said. "We were letting it happen while we were sitting and reading Facebook and watching reality TV."

Then came a subway ride that exposed the wounds of a divided electorate in this summer of discontent.

"I feel like you guys have left the party," interjected Gina Mitten, 52, a state representative and Clinton delegate from Missouri who overheard Costello talking to a reporter. She shouted as the train roared toward the arena where Hillary Clinton would make history later that night.

"If you all want us to come back to you," sniped Sanders backer Douglas Stoll, a 31-year-old North Carolina social worker seated nearby, "what do you want us to come back to?"

That's the central question left hanging by the week's events in Philadelphia. Sanders didn't win the nomination, but neither did Clinton win the loyalty of his flock. This insurgency, they say, is not going to pass.

The divide among Democrats in Philadelphia reflected long-simmering anger as voters despair over an economy and political system they feel have abandoned them.

Sanders loyalists protested day and night against Clinton, jeering even when Sanders mentioned her name. Clintonites fretted over winning over the disaffected by November, fearful of handing victory to GOP tycoon Donald Trump.

Comparable rancor had erupted in Cleveland a week earlier, in a chaotic GOP convention that itself was the product of factional discord. In that case, Trump is the insurgent who beat the party establishment, riding a wave of Americans who don't think the country is moving in the right direction.

In Philadelphia, the anger cut largely along generational lines. Those born after Clinton's baby-boom generation were far more likely to be feeling the Bern.

"It's clear that the Hillary Clinton campaign is the last hurrah of a generation," said James Galbraith, a University of Texas professor who at 19 was the policy brain for George McGovern's insurgent campaign in 1972. "The movement mobilized by Sanders has a specific set of policy goals, and it is a coming generation for sure."

Day one was about to devolve into a shout-fest.

DNC chief Debbie Wasserman Schultz had resigned hours earlier after a WikiLeaks email leak suggested party leaders had conspired to defeat Sanders in the primary.

This was all anyone was talking about Monday morning. But Gwen Snyder, 30, found time at her Center City hotel to pause and reflect.

Snyder graduated from Swarthmore College in 2008, into an imperfect storm: The global economy was in free fall. She has just finished her master's degree in public policy and is $100,000 in debt.

"Nobody in my generation outside of Wall Street has a decent retirement setup for themselves," said Snyder, executive director of Jobs With Justice in Philadelphia.

It was back in January, Snyder said, that she decided to support Sanders. He didn't have a chance, she figured. But he was on the right side: far to the left of Clinton.

"I just assumed that America would hear socialist and think crazy or un-American," Snyder said.

Sanders opposed global trade pacts blamed for gutting U.S. manufacturing; backed a $15 federal minimum wage; demanded that Washington be cleansed of big-money donor influence; and called for subsidizing the cost of college.

Snyder was shocked as Sanders began chalking up one primary or caucus win after another - even an upset in Michigan, where Clinton had been expected to defeat her opponent with the support of her African American base.

Formerly apolitical friends were suddenly abuzz over Sanders. Snyder found only three words to describe what that felt like at the time:

"What the f-?"

Sanders raised his fist Monday at midday, and leaned into a microphone as some 1,846 delegates representing 13 million voters greeted him like a rock star.

"Feel the Bern! Feel the Bern!" they chanted as he took the stage of the Convention Center.

Sanders' pledged delegate total had come surprisingly close to Clinton's 2,205. He had done so with the support not just of fringe activists but of Democrats across the spectrum who felt his message of refocusing the party on working Americans had been neglected for too long.

But party rules allowing insiders known as superdelegates to vote any way they liked gave Clinton an even bigger bloc of support, and enraged the Sanders camp.

"You have heard me say a million times that this campaign is not just about electing a president," Sanders bellowed as his apostles cheered. "It is building a movement to transform this country."

Still, Sanders urged them to vote for Clinton, the woman he had portrayed for months as part of the problem.

The room turned borderline mutinous. So what if Clinton, as Sanders said, was the only way to beat Trump, "a bully and a demagogue."

"So is Hillary!" some in the crowd shouted.

"Hillary has insulted us!"

The barbs, wails, and jeers continued.

Georgia's Rep. John Lewis knows more than most about fighting for change.

"Years ago, during the height of the civil rights movement, I was beaten, bloodied," Lewis said on a sweltering Tuesday morning at a gun-control rally along the Benjamin Franklin Parkway. He spoke of being pummeled by Alabama state troopers in 1965 on Bloody Sunday as he and others marched and prayed for blacks to win the right to vote.

"Almost died on that bridge," Lewis said. "But I never lost hope. Never gave up."

Lewis is now one of the party's eldest statesmen. As he left the rally, he was asked if he could recall any other convention with as much discord as this year's.

"We had it in '68 in Chicago," Lewis said. "We had it in '64 in Atlantic City."

Tom Leonard, chairman of Obermayer Rebmann Maxwell & Hippel L.L.P., was a McGovern activist and is now the head of Clinton's national finance committee. He calls Sanders "a remarkable candidate" and thinks that all parties have to go through discord:

They are "going to have a center, a left, and a right, and there's going to be tension, and you have to sort through those issues each election cycle," Leonard said.

How to bridge the chasm by November? Just before joining the gun-control rally, Deborah Pignatelli of New Hampshire had been talking with other Clinton delegates about just that thing.

"We're waiting and hoping and working hard to include the Bernie Sanders delegates and supporters," said Pignatelli, 68, a retired elected official.

Michelle Dunston is 28, African American, and a nurse living in one of Pennsylvania's poorest cities, Chester.

She watched her two children, ages 3 and 8, hop through jets of water at Dilworth Park on Wednesday while, a block away, Sanders protesters demonstrated loudly on Thomas Paine Plaza. Many wore sandals, ragged T-shirts, and had the scruffly looks of advocates not new to this sort of scene.

Through it all, she was wistful about Sanders.

"He's just somebody that I thought was for the people," she said. "I fear for my son to grow up as a black man. I'm just hoping for the justice system to be on our side more."

Across the way, third-party Green candidate Jill Stein showed up at the protest. She made her way only with the help of a ring of cops clearing her crowded path.

Embittered Sanders loyalists talked about voting for Stein in November, despite predictions that this could lead to a Trump win.

Walking away from the demonstration, Stein voiced the double-edged frustration of this election year: "Donald Trump is a crisis. Hillary Clinton is a crisis."

"It's a bittersweet thing," Costello said Thursday after returning home to Arizona. "I'm sad that a miracle didn't happen."

A lifelong Democrat, she had never before taken off work to protest. Had never imagined herself marching for political change. But she is committed to keep pushing for a progressive vision to a party she believes has dropped too many Americans off its radar.

In becoming active for Sanders, she has discovered a community.

"These are attorneys, accountants, physicians," she said - all now working to elect progressive school boards, mayors, and members of Congress. "We speak for all in the country."

215-854-2431 @Panaritism