Republican 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. Senator Lindsey Graham has served on Capitol Hill for a quarter of a century, yet the South Carolina Republican barely cracks 1 per cent in the polls. But Ben Carson, a soft-spoken retired surgeon with 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.
On the left, Sanders has blazed a similar outside trail. The self-described socialist Senator from Vermont is giving Clinton a scare. He has drawn huge overflow crowds.
"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 levelling with voters."
Clinton has been treading carefully in responding to the populist threat Sanders poses, but has been laying out a progressive agenda on immigration reform, voting rights, college affordability, regulating the financial sector and economic concerns, such as expanding paid leave. A Franklin Pierce University/Boston Herald poll had Sanders at 44 per cent to Clinton's 37 per cent 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 gain with minority groups.
The outsider dynamic is more pronounced on the Republican side, where Trump and other candidates are galvanising 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 Senator 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.
Insider candidates are by no means out of the game.
Former Florida Governor Jeb Bush is the clear fundraising leader.
He is seen by many activists and analysts as the most likely eventual nominee. Florida Senator Marco Rubio is also is seen as a plausible nominee. Wisconsin Governor Scott Walker has polled at or near the top all year in Iowa and is laying the groundwork for an aggressive, national campaign. And Ohio Governor John Kasich has risen in New Hampshire on the strength of his debate performance.
Flying high
Ben Carson
• 63, retired neurosurgeon
• From humble background, rose to be director of pediatric neurosurgery at Johns Hopkins Hospital. Favourite of conservative activists. He has spent 36 years in the private sector.
Carly Fiorina
• 60, former CEO of Hewlett Packard
• From Austin, Texas, she dropped out of university to pursue a career in business and became the first woman to be appointed to head one of the top 20 US companies. She was eventually fired from the board but walked away with a US$21 million payout.
Bernie Sanders
• 73, senator for Vermont
• Born in New York, Sanders is a self-described democrativ socialist and has been drawing enthusiastic crowds. He has represented Vermont as a senator since 2007. He was previously a congressman and mayor for Vermont.
