Vote on the primary election shockers that toppled frontrunners, flattened incumbents, and rewrote the political map — which upset was the biggest of them all?
What counts: Ranked by the scale of the shock: how big a polling deficit was overcome, whether a sitting officeholder was toppled, and how much lasting impact the result had on national politics. All polling deficits and vote margins are rounded, approximate figures drawn from historical polling and election dat
Barack Obama over Hillary Clinton (2008)
A first-term senator with a funny name took down the most powerful machine in Democratic politics, starting with a stunning Iowa caucus win that shattered Clinton's air of inevitability. The race stretched all the way to June, but Obama's coalition of young voters and caucus-stat
Year: 2008Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: 15 %Shock Factor: 8/10Lasting Impact: 10/10Margin of Victory: 2 %
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Donald Trump wins the 2016 GOP Primary
A reality-TV billionaire with no political experience steamrolled sixteen seasoned governors and senators, dominating debates and media coverage while mocking rivals with nicknames. Pundits predicted his collapse after every controversy, yet he kept winning and clinched the nomin
Year: 2016Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: —Shock Factor: 9/10Lasting Impact: 10/10Margin of Victory: 19 %
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Dave Brat over Eric Cantor (2014)
The sitting House Majority Leader, a fixture of national Republican politics, lost his Virginia primary to a little-known economics professor who spent barely $200,000. Cantor outspent Brat roughly 40-to-1 and still lost by 11 points, the first time a House Majority Leader had ev
Year: 2014Race Type: House PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 30 %Shock Factor: 10/10Lasting Impact: 8/10Margin of Victory: 11 %
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Alexandria Ocasio-Cortez over Joe Crowley (2018)
A 28-year-old former bartender with a shoestring budget knocked off the fourth-ranking House Democrat and a man some saw as a future Speaker. Crowley didn't even show up to a debate, sending a surrogate instead — a decision that became a symbol of establishment complacency. AOC's
Year: 2018Race Type: House PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 35 %Shock Factor: 9/10Lasting Impact: 9/10Margin of Victory: 15 %
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Bernie Sanders wins Michigan (2016)
Polling averages had Hillary Clinton up by more than 20 points heading into Michigan, and most networks had all but called the race. Sanders pulled off one of the greatest polling misses in primary history, eking out a narrow win that proved his campaign wasn't just a protest mov
Year: 2016Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: 20 %Shock Factor: 9/10Lasting Impact: 6/10Margin of Victory: 2 %
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Ned Lamont over Joe Lieberman (2006)
An anti-Iraq War political newcomer with no prior office toppled Al Gore's former running mate and a three-term senator in Connecticut's Democratic primary. Lieberman refused to accept defeat, running and winning as an independent that fall, but the primary loss marked the first
Year: 2006Race Type: Senate PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 15 %Shock Factor: 7/10Lasting Impact: 6/10Margin of Victory: 4 %
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Eugene McCarthy shocks LBJ in New Hampshire (1968)
A little-known antiwar senator held a sitting president to a shockingly narrow 7-point win in New Hampshire, a result the press treated as a moral defeat for Lyndon Johnson. Robert Kennedy entered the race days later, and Johnson stunned the country by announcing he wouldn't seek
Year: 1968Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: —Shock Factor: 9/10Lasting Impact: 9/10Margin of Victory: 7 %
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Estes Kefauver upsets Harry Truman (1952)
A crime-fighting Tennessee senator best known for televised Mafia hearings beat a sitting president in the New Hampshire primary by double digits. Truman, humiliated, announced weeks later he would not seek another term, cementing New Hampshire's role as a presidential bellwether
Year: 1952Race Type: Presidential PrimaryToppled Incumbent: ✓Polling Deficit Overcome: —Shock Factor: 8/10Lasting Impact: 7/10Margin of Victory: 10 %
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Gary Hart surges past Walter Mondale (1984)
Written off as an afterthought with single-digit polling, Hart rode a wave of late momentum to a decisive New Hampshire win over Mondale, the establishment's chosen heir to Carter-era Democratic politics. His 'new ideas' message briefly made him the frontrunner before Mondale's f
Year: 1984Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: 30 %Shock Factor: 8/10Lasting Impact: 5/10Margin of Victory: 9 %
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Pat Buchanan rattles George H.W. Bush (1992)
A conservative commentator with no elected experience challenged a sitting Republican president fresh off Gulf War victory and still took 37% of the vote in New Hampshire. The result exposed deep conservative discontent with Bush's broken 'no new taxes' pledge and previewed the p
Year: 1992Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: —Shock Factor: 6/10Lasting Impact: 4/10Margin of Victory: 16 %
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Rick Santorum's Iowa nail-biter (2012)
Written off for dead after barely registering in national polls for months, Santorum's shoestring, church-basement campaign surged in Iowa's final days. He edged out Mitt Romney by a mere 34 votes out of over 120,000 cast, a margin so thin it took weeks to certify. It remains one
Year: 2012Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: 15 %Shock Factor: 7/10Lasting Impact: 4/10Margin of Victory: 0.03 %
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Christine O'Donnell over Mike Castle (2010)
A little-known Tea Party activist with a thin resume upset a nine-term congressman and popular former governor who was heavily favored to win Delaware's Senate seat. National Republicans were stunned and furious, correctly predicting O'Donnell's general-election collapse in a sta
Year: 2010Race Type: Senate PrimaryToppled Incumbent: —Polling Deficit Overcome: 20 %Shock Factor: 8/10Lasting Impact: 5/10Margin of Victory: 6 %
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Richard Mourdock over Dick Lugar (2012)
A six-term senator and one of the Senate's most respected foreign policy voices lost to a state treasurer who painted him as too willing to compromise with Democrats. Mourdock's blowout 21-point win showed how thoroughly the Tea Party wave had turned bipartisanship into a primary
Year: 2012Race Type: Senate PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 10 %Shock Factor: 7/10Lasting Impact: 4/10Margin of Victory: 21 %
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Ayanna Pressley over Michael Capuano (2018)
A ten-term incumbent with a solid progressive record still lost to a Boston city councilwoman running on generational and representational change within his own coalition. Pressley's decisive 17-point win made her part of a wave of insurgent Democratic women reshaping safe-seat p
Year: 2018Race Type: House PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 15 %Shock Factor: 7/10Lasting Impact: 6/10Margin of Victory: 17 %
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Jamaal Bowman over Eliot Engel (2020)
A middle school principal ousted the 16-term chair of the House Foreign Affairs Committee after Engel was caught on a hot mic explaining why he wanted to speak at a press conference: 'If I didn't have a primary, I wouldn't care.' That gaffe, paired with Bowman's grassroots organi
Year: 2020Race Type: House PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 20 %Shock Factor: 7/10Lasting Impact: 6/10Margin of Victory: 15 %
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Cori Bush over William Lacy Clay (2020)
Bush had already lost to the Clay family's St. Louis political dynasty twice before finally beating William Lacy Clay Jr. in 2020, ending 52 years of Clay family control over the seat. Her narrow win, built on Black Lives Matter organizing following the Ferguson protests, turned
Year: 2020Race Type: House PrimaryToppled Incumbent: ✓Polling Deficit Overcome: 15 %Shock Factor: 7/10Lasting Impact: 6/10Margin of Victory: 3 %
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John McCain routs George W. Bush in New Hampshire (2000)
McCain's 'Straight Talk Express' bus tour turned a supposedly one-sided New Hampshire primary into a 19-point rout of the establishment's anointed candidate. It briefly made McCain the GOP frontrunner and forced a bruising South Carolina counterattack that effectively ended his c
Year: 2000Race Type: Presidential PrimaryToppled Incumbent: —Polling Deficit Overcome: 10 %Shock Factor: 6/10Lasting Impact: 4/10Margin of Victory: 19 %
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Joe Miller upsets Lisa Murkowski (2010)
A sitting, well-funded incumbent senator from a prominent Alaska political family lost her own party's primary to a Tea Party-backed newcomer she had badly underestimated. Murkowski refused to accept the result, mounting a historic write-in campaign and becoming just the second s
Year: 2010Race Type: Senate PrimaryToppled Incumbent: ✓Polling Deficit Overcome: —Shock Factor: 8/10Lasting Impact: 5/10Margin of Victory: 2 %
added by IJR
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