Fresh-faced and only 37, Boyle combines a working-class story - the son of a SEPTA janitor and an Olney crossing guard - with degrees from Notre Dame and Harvard, and an ease talking politics or policy. After winning the primary in a Democratic stronghold that includes Northeast Philadelphia and much of Montgomery County, Boyle is favored in November against Republican Dee Adcock, a Montgomery County businessman.
They are running for the seat that five-term incumbent Allyson Y. Schwartz gave up to launch her run for governor, which ended Tuesday in her defeat for the Democratic nomination by Tom Wolf.
Boyle cleared what is likely his toughest hurdle Tuesday when he defeated former U.S. Rep. Marjorie Margolies - an ally of the Clintons and mother-in-law to Chelsea Clinton - State Sen. Daylin Leach, and physician Valerie Arkoosh. Those three split votes in Montgomery County while Boyle performed respectably there. In Philadelphia, though, he blistered the field.
His victory was helped by Build a Better PA, a recently formed fund that spent at least $342,500 - and likely more - on television ads, but whose donors' identities remain a secret. The super PAC has an address in Washington, a treasurer in New Jersey, and heavy backing from Philadelphia unions. The bulk of its money - "north of" $200,000 - came from Local 98 of the International Brotherhood of Electrical Workers, said Dougherty, the union's business manager.
"We play by the rules. Whatever the rules allow," Dougherty said Wednesday. "Brendan was running against three millionaires. I wanted to make sure he had the same resources, and I wanted to make sure that his message was told."
Boyle's message - built around his personal story and the middle-class worry gripping so many - showcased some of the political talent that has Dougherty raving and predicting big things.
While much of the media focused on Margolies' ties to the Clintons, Boyle stressed his family's humble roots in Northeast Philadelphia.
His father was a longtime Teamster. His mother, who died in October, shortly before Boyle's first child was born, was a crossing guard and a member of AFSCME for nearly 30 years.
"While I've never been in a union myself, it is a part of who I am," Boyle said Wednesday morning, seamlessly weaving his upbringing into his political message. "I was born into a labor family. The hardworking, hard-pressed middle class is working more today for actually less pay and slipping behind, and I'm someone who completely understands that."
As for his education, Boyle said he relied on student loans and scholarships, and was the first in his family to go to college.
Sitting in a coffee shop in Liberty Place, the youthful-looking Boyle was clean-shaven even after just two hours of sleep, his phone insistently chiming as he drank from a sizable plastic cup of Diet Coke at 10:30 a.m.
He recounted an internal poll, roughly 11 months ago, that found him trailing in the primary by 32 points. To make up the gap, he said, he raised "sufficient" money - though not as much as his competitors.
He also put roughly $100,000 of his own money into his campaign, including $40,000 on May 7, two weeks before primary day.
Boyle, however, said money alone won't decide campaigns. He pointed out that his opponents out-raised him and some also had aid from outside groups.
Instead, he emphasized the blue-collar effort that included his knocking on doors and inviting voters to meetings over pizza and soup - 225 voter events in all, he said - that ended with a 13-hour stint shaking hands at a Northeast polling station Tuesday.
"The Boyle brothers win elections," said David Dunphy, a Democratic political operative not working in this campaign. "Nobody outworks them."
Boyle's brother Kevin, also a state representative, is his closest political adviser.
Asked about Build a Better PA, Brendan Boyle said he didn't know what it was going to do or when. Such groups are barred from coordinating with candidates' campaigns. He referred to news reports he had read when asked about who funded the organization. The Philadelphia Daily News first reported the PAC's existence.
"We were hoping organized labor would go the extra step, but in the end really had no idea until it actually happened what they would do," Boyle said.
He called campaign finance laws "insane" and said he would support a constitutional amendment to allow tougher regulations on political spending. Court rulings have loosened campaign laws, allowing donors to give unlimited amounts to Super PACs.
Build a Better PA was chaired by Wayne Miller, the head of the local sprinkler fitters union, according to Dougherty, who stressed that Miller ensured "there were a tremendous amount of experienced professionals making sure" the organization followed the law.
The PAC - governed by federal, not state, law - has had to disclose its spending. But it won't be required to disclose its donors in full until this summer.
In its only campaign finance report to date, it reported no paid staff and said it was relying on "consultants and volunteers." It had no money through March 31, the end date of the report.
The next day, Dougherty's union gave it $100,000 - an amount that won't show up until the next set of disclosures is released, in July.
Other supporters of the super PAC include "the labor movement and some of the friends of the labor movement, and some of the friends of Brendan," Dougherty said Wednesday. Many of them gave the $5,000 maximum allowed by law to Boyle's campaign, but were also allowed to give as much as they wanted to the super PAC.
Asked whether the fund would remain active after the primary, Dougherty said, "Of course." Millionaires and billionaires, he said, can't be allowed to play by a different set of rules.
A Boyle victory in November would leave Montgomery County, the third most populous county in the state, without a member of Congress from within its borders. Schwartz was a five-term incumbent.
Boyle pointed out that he already represents some of Montgomery County in his state legislative district.
Adcock, the Republican nominee from Montgomery County, said he shouldn't be counted out and warned against a national slide from capitalism toward socialism.
"It's now or never if we're going to move our country in the right direction," he said, pledging to "revive" the American dream.
But an Adcock win would require a massive upset. Democrats dominate the district and Republicans haven't won the seat since the 1990s.
With his youth and a safe seat potentially his for years to come, Boyle could have time to build seniority and perhaps grab a foothold in party leadership, something Philadelphia doesn't currently have.
"If you see a young guy who's smart, who's aggressive, but at the same time has sort of the skill set to tactfully play the game and move up into leadership ... that's the kind of guy you want on your side," Dunphy said.
Of course, lofty predictions are easy after victory.
Still, Dougherty said that while Philadelphia Democrats Robert Brady and Chaka Fattah "understand the system," Boyle would be "a different type of congressman."
"He's going to be able to articulate and argue and represent anything that comes down his pike," Dougherty said.
For all his focus on humble roots, Boyle did not shy away from such lofty ambitions. He said he hoped to help elevate the public profile of the Philadelphia-area delegation to one that befits a city of its size.
He has allies cheering him on, and ready to offer top-dollar help.
Contributing to this article were Inquirer staff writers Bob Warner, Troy Graham, and Tricia L. Nadolny.