For the past three decades, there has been a rhythm in presidential politics. Every four years, in the summer before Iowa and New Hampshire vote, some candidate comes out of nowhere, surges in the polls, gets buzz, and then eventually returns to nowhere.

As self-described socialist Bernie Sanders and reality television star Donald Trump surge into second place in the Democratic and Republican presidential contests, some may wonder what’s happening to American politics.

This is what UCLA professor Lynn Vavreck dubs the “discovery, scrutiny, decline” pattern. Party activists discover a shiny new candidate as an alternative to the race’s front-runner, usually when the campaign is just beginning. The insurgent faces press scrutiny and then, typically, declines.


“It is not unlike products that debut and get people to try them out,” said Vavreck. “But what news coverage giveth, news coverage taketh away.”

Four years ago, everyone was talking about former Minnesota US representative Michele Bachmann. From April to June 2011, Bachmann had picked up 8 percentage points in a University of New Hampshire poll. She was in second place behind former Massachusetts governor Mitt Romney. She would go on to perform so badly in the Iowa caucuses that she didn’t even make it to the New Hampshire primary.

Romney might not have been too worried about Bachmann because he had seen the pattern before. In 2007, he was the one having his moment in the summer sun. In June of that year, he led the field in New Hampshire with his highest poll numbers of the year. Behind Romney was former Tennessee senator Fred Thompson, who many thought could very well be the eventual nominee; in fact, the eventual winner was John McCain. On the Democratic side, former New Mexico governor Bill Richardson was the on the move, picking up 6 percentage points in three months and sliding into third place behind Hillary Rodham Clinton and Barack Obama.


At this point in 2004, former Vermont governor Howard Dean tied former Massachusetts senator John Kerry for the first time in New Hampshire and, like Sanders, was drawing huge crowds in liberal cities across the country.

In 1999, former New Jersey US senator Bill Bradley was getting the type of media attention and positive poll numbers in his race against Al Gore that Republican Pat Buchanan got against Kansas senator Bob Dole in the early months of the ’96 race.

In the summer of 1991, Mario Cuomo and Al Gore — neither of whom ultimately competed in the ’92 race — were well ahead of Bill Clinton. In the summer of 1987, the Democratic front-runner was Jesse Jackson.

In June 1983, The Washington Post thought the fact that California US Senator Alan Cranston beat Walter Mondale in a Wisconsin straw poll was worthy of a story. (At the time, Ohio US Senator John Glenn was tied with Mondale, the eventual Democratic nominee in ’84.)

This phenomenon usually happens in the summer, not earlier or later, because this is the time when candidates begin to actively campaign and activists are opened minded, according to University of Arizona professor Barbara Norrander, the author of “The Imperfect Primary.”

“A candidate catches the public or media eye with a candidacy announcement, win in a straw poll, good debate performance, etc.,” Norrander said. “This leads to mostly positive news coverage and an increase in poll numbers.”


The bad news for Trump and Sanders: If history is any guide, eventually their bubbles could burst.

Duke University professor John Aldrich cautions voters not to get too excited or worried by this summer’s boomlets from Trump and Sanders.

“There has been very close to no looking into who the contenders are as contenders at this point, nor what they might stand for, beyond the real activist types,” Aldrich said. “And no one can figure who a likely voter is at this point, beyond the most general sort of way, and so pollsters ask a lot more of the uninformed and uninterested people.”

YEAR SUMMER BEFORE BUZZ CANDIDATE EVENTUAL NOMINEE 1984 Alan Cranston, John Glenn Walter Mondale 1988 Jesse Jackson Michael Dukakis 1992 Al Gore, Mario Cuomo Bill Clinton 1996 Pat Buchanan Bob Dole 2000 Bill Bradley Al Gore 2004 Howard Dean John Kerry 2008 Mitt Romney, Bill Richardson John McCain, Barack Obama 2012 Michele Bachmann Mitt Romney 2016 Bernie Sanders, Donald Trump ?????????????

James Pindell can be reached at James.Pindell

@globe.com or on Twitter @jamespindell, or subscribe to his daily e-mail update on the 2016 campaign at bostonglobe.com/groundgame.