But from 1980 through 2004, the only race on either side that remained truly undecided through the final day of voting was Walter Mondale’s 1984 Democratic victory over Gary Hart. Among Democrats, Edward M. Kennedy in 1980, Jesse Jackson in 1988, and Edmund G. (Jerry) Brown in 1992 continued long-shot bids through all the primaries, but by the end more as candidates advancing a message than viable alternatives: Brown, for instance, didn’t win a state after March. (Even Kennedy distantly trailed Carter in delegates.) In the 2000 and 2004 races, the last major opponent to the eventual Democratic nominee conceded in March.
Likewise, though George H.W. Bush in 1980 ran against Reagan until late May, he trailed hopelessly behind in delegates. Since then, March has been the cruelest month for GOP challengers: In the five contested GOP races since 1988, the last viable alternatives to the eventual nominee all conceded then.
The epic 2008 Democratic primary between Hillary Clinton and Barack Obama hinted at a new pattern. That race became the first since Mondale/Hart to remain competitive through the entire calendar. Now each side’s 2016 contest could persist that long. Trump will need to scratch for every delegate to secure a first ballot majority. And while Sanders may be evolving into something between a message candidate and a viable alternative, he’s likely to win enough states in May to press Clinton through California on June 7 and the District of Columbia one week later. If he does, it will mean that three of the past five nominating fights will have gone the distance after just one did from 1980 through 2004.
Factors distinctive to each race partly explain this change. In 2008, Clinton and Obama were uniquely matched in their strengths; conversely, the inability of Clinton and Trump to seal the deal largely reflects their current weaknesses (quantified in historically high unfavorable ratings).
But deeper changes are involved too. Money and media attention are to campaigns what fuel and oxygen are to fire. Trailing candidates used to quit because their money and media coverage dried up. Now candidates who cross a modest viability threshold can generate nearly unlimited amounts of both.
Small donations from online donors allow trailing candidates to more easily finance a campaign than before. In earlier years, Sanders, after his big March 15 losses, probably could have continued only by taking out a personal bank loan, a daunting prospect that often convinced candidates to quit. Instead he sent out a fund-raising email. “The fundamental change that has allowed it to continue so long is that today someone can raise extraordinary amounts of money without resorting to the old traditional fund-raising,” says Tad Devine, Sanders’s senior strategist. For establishment candidates, Super PACs provide an alternative financial lifeline.