WASHINGTON — This has become the summer of the political outsider, as a cast of interlopers upend and dominate the presidential nominating process in both parties.

The surging candidacies of Donald Trump and Bernie Sanders are fueled by people’s anger with the status quo and craving of authenticity in political leaders. Across the ideological spectrum, candidates are gaining traction by separating themselves from the political and economic system that many everyday Americans see as rigged against them.

“There are a lot of voters who are exceptionally frustrated with traditional politics and politicians and who quite simply feel failed by the system,” said pollster Geoff Garin, who advises Priorities USA Action, a super PAC supporting Democratic front-runner Hillary Rodham Clinton. “A lot of this anger crosses party lines in the sense that it is directed at what people see as a concentration of wealth and power that leaves them holding the short end of the stick.”

Consider recent developments in the Republican race. Rick Perry was governor of Texas for 14 years and had an enviable jobs record to boot, but his presidential campaign is running on fumes. Sen. Lindsey Graham has served on Capitol Hill for a quarter century, yet the South Carolina Republican barely cracks 1 percent in the polls.

In stark contrast, Ben Carson, a soft-spoken retired surgeon with far more expertise in separating conjoined twins than brokering trade agreements, is surging in recent polls and turned out one of the biggest campaign crowds yet in Des Moines last week. Carly Fiorina, a businesswoman who has never held elected office, is also on the upswing.

Then there is Trump. The brash billionaire, who loudly brands politicians as “stupid” and “losers,” has rocketed to front-runner status.

On the left, Sanders has blazed a similar outside trail. The self-described socialist senator from Vermont, who routinely scolds the Washington and Wall Street establishments, is giving Clinton a scare. He has drawn massive overflow crowds — and on Wednesday, he surpassed Clinton in a New Hampshire poll for the first time.

“There’s a longing for real authenticity in politics today,” said Tad Devine, a veteran Democratic strategist who is advising Sanders. “People feel that the candidates are too manufactured, there’s not enough spontaneity. They want someone who, even if they don’t agree with them, is telling it like they see it, really leveling with voters. I see that with Bernie and I think with Trump, too. It’s resonating very powerfully.”

Clinton has been treading carefully in responding to the populist threat Sanders poses, but has spent the summer laying out a progressive agenda on immigration reform, voting rights, college affordability, regulating the financial sector and economic pocketbook concerns, such as expanding paid leave.

Sanders saw his first edge over Clinton on Wednesday, when a Franklin Pierce University/Boston Herald poll had him at 44 percent to Clinton’s 37 percent among likely Democratic primary voters in New Hampshire, home to the first primary.

But Clinton has a decisive lead in national polls, as well as in Iowa, which hosts the nation’s first caucuses. Support for Sanders is concentrated among highly educated white liberals, and he has struggled to make inroads with minority groups.

The outsider dynamic is more pronounced on the Republican side, where Trump and other candidates are galvanizing conservative activists while a handful of governors and senators are splitting the party establishment vote.

Carson and Fiorina have seen their stock rise following last week’s first primary debate, as has Sen. Ted Cruz of Texas, who despite a career in politics has positioned himself firmly as anti-establishment.

Post-debate polls show these candidates gaining ground. In Iowa, a CNN poll released Wednesday shows Trump leading at 22 percent and Carson in second at 14 percent. Wisconsin Gov. Scott Walker, who had been the Iowa front-runner, was third at 9 percent, followed by Cruz and Fiorina with 8 percent and 7 percent, respectively.

In New Hampshire, the Franklin Pierce University/Boston Herald survey had Trump in the lead with 18 percent, followed by former Florida Gov. Jeb Bush in second with 13 percent and Ohio Gov. John Kasich in third with 12 percent. Cruz and Fiorina are fourth and fifth with 10 percent and 9 percent.

“There’s a disquiet, discomfort and angst that so many people are feeling,” said GOP pollster Whit Ayres, who advises Florida Sen. Marco Rubio. “They’re scared economically, they’re scared about what’s happening with our adversaries and it makes them really, really uncomfortable with where the country’s going and where the leaders are going.”

Insider candidates are by no means out of the game. Bush is the clear fundraising leader and holds his own in polling. He is seen by many Republicans and Democrats as the most likely eventual nominee. On Tuesday, Bush Instagrammed a photo of a turtle — “joyful tortoise,” read his caption — as a metaphor for his position in the contest.

Rubio gave what many Republican insiders considered a sparkling debate performance and also is seen as a plausible nominee. Walker has polled at or near the top all year in Iowa and is laying the groundwork for an aggressive, national campaign. And Kasich, a late entrant, has risen in New Hampshire on the strength of his debate performance as well as a television advertising campaign in the state by his allied super PAC.

But it’s the fiery insurgents — especially Trump, but also Fiorina and others — who are generating buzz and media attention at the moment, drowning out and frustrating some of their more established opponents.

Among the victims is Louisiana Gov. Bobby Jindal, who has served in government nearly his entire adult life and sees the presidency as the next step on his career ladder. But he has failed to break out of the bottom of a 17-candidate pack.

“The media is glued to everything Donald Trump says,” Jindal complained to reporters this week.

History is filled with examples of outsider candidacies that galvanize activists but run out of gas.

“Wherever the insurgency was — and it didn’t matter which party it was in — the establishment had almost ironclad control over the rules, over the money,” said Democratic strategist Joe Trippi, who ran Howard Dean’s 2004 campaign. “They could form a firing squad and just hail ammo at you until you drop.”

But now, Trippi said, social media and digital communications make it far easier for outsiders to get their message out and mobilize supporters. “Both parties are losing control,” he said.

Officials in the Bush, Walker, Rubio and Kasich campaigns say they are not concerned about Trump’s summer rise. It is only August, after all, and they argued that the race will remain unsettled through the fall.

“We’ve always thought this race was wide open and the events of the last week tell us clearly that it is,” said John Weaver, chief strategist to Kasich. “There is no front-runner.”

Rick Wilson, a Republican consultant who is not aligned with a presidential campaign, said voters eventually will gravitate toward the more serious contenders.

“I think that after people get their yips out about Trump, people are going to ask, ‘How do we have the right person to post up against Hillary Clinton? Who can break the code?'” Wilson said. “A lot of the Trump stuff is an emotional response to being furious about the establishment, about immigration, all these other sensations that are not illegitimate feelings but that are not going to be politically viable for the long haul.”

Anthony Scaramucci, one of Walker’s top national fundraisers, foresees a calming of the race that could benefit a candidate like Walker. “I think the cream will rise to the top and Governor Walker will be way more effective with less people on stage,” he said. “He’s more steak than sizzle.”

But other Republicans believe the tempest that Trump has whipped up will not die down. One of them is Cruz, who is among the best funded candidates and is building a nationwide grassroots organization. Cruz has refrained from attacking Trump, setting himself up to capture the anti-establishment vote when it looks for its final home this winter.

“I don’t think it is necessarily a majority of either party that is fueled by fury,” Garin said, “but there are a lot of furious voters out there who feel completely alienated from and let down by politics as usual.”