Political Momentum: Is That a Real Thing?

Bernie Sanders says he's got it. So does Ted Cruz. But will their victories in recent primaries translate into a big win in next week's New York contest? Will undecided voters jump on the bandwagon, so to speak, and is the psychological effect some call political momentum real or just imagined?

Social scientists say the idea of "social herding" is a long-standing one and does have some observational and experimental basis. People often gravitate to things that are popular precisely because they are popular. That includes consumer products as well as political candidates.

Neil Malhotra is a professor of political economy at Stanford University. He's written about political momentum and the bandwagon effect. He says it often occurs during primary elections when voters' political identities haven't hardened into either Democratic or Republican party affiliations.

"Voters don't have as much to go on in the primaries," Malhotra said. "There's no incumbent and party IDs are the same."

In general elections, the number of undecided voters has shrunk considerably, making it more difficult to take advantage of momentum.

"There's not many people on the margins that could go either way," he said.

Malhotra believes there are several reasons why primary voters may pick the front-runner.

"The first is the idea of normative social influence, you don't want to be excluded so you conform to not be isolated," he said. Call it peer pressure.

"The second mechanism is informational social influence; if a lot of people are doing something, you make the inference that its probably a good thing to do," he added.

The third reason is something called cognitive dissonance reduction.

"It's the story of the sour grapes," Malhotra explained. "I can't get them, so I say I don't want them. Instead, I turned the sour grapes into a sweet lemon. You change your mind and convince yourself to support a candidate because they are ahead. You can convince yourself that you really like them."

Sanders, who was far behind Democratic front-runner Hillary Clinton in public opinion polls last fall and even after the initial primaries in January, has narrowed the gap with victories in seven of the last eight primaries. However, those wins were in smaller states with fewer minority voters, who are traditional supporters of Clinton. Clinton still holds a commanding lead in pledged delegates for the Democratic nomination.

"He's the guy that we would say there has been a momentum swing for them," said Patrick Kenney, dean of the college of liberal arts at Arizona State University and a political scientist who has also written on the bandwagon effect in elections.

On the Republican side, however, where Donald Trump continues to lead despite recent gains by Cruz, Kenney said social scientists are a bit stumped.

"We have no good explanation for Trump," Kenney said. "We will have to wait and see the data on it."

Kenney said that Cruz's momentum in a few recent states may be coming from "strategic voters" who don't necessarily support Cruz's policy ideas, but are worried that Trump would be a worse choice.

Kenney said that American voters are often swayed during primaries because most do not follow politics as closely as voters in other countries. Political momentum gets a boost by the emotional attachments formed by some voters with a candidate, something that may be bringing in younger, first-time voters to Sanders' campaign.

"People who love democracy would like to see more strategic or policy voting, but most data shows that isn't the case," Kenney said. "Americans on average are not big daily consumers of politics. Things pop up for them and they have to make a decision. They're not interested in it. The party is such an easy cue, but in primary, there's no party there."

June 15, 2012 --

No matter who comes out ahead in this year's race to the White House, there's no doubt that there will be one big winner coming out of this election: advertisers. With the amount of money flowing into the coffers of the campaigns of both the incumbent, President Barack Obama, and challenger, Governor Mitt Romney, this election should break records for the amount of cumulative ad spending by both campaigns as well as outside groups. According to National Journal's Reid Wilson, even with the election still a little more than four and a half months away, ad spending has already topped $100 million. Despite all the resources pumped into getting a particular campaign's message to voters, how well a particular ad buy will resonate with audiences is anyone's guess. As the old saying goes in the industry, "half of all advertising is a waste of money; we just don't know which half." Presidential campaigns and outside groups could take a lesson from the past, however, by examining some of the most successful ad spots in U.S. presidential election history. In this slideshow, take a look at some of the ads that made an impression that counted one way or another.

PHOTOS: Campaign Posters Through History

'I Like Ike' Television advertising is expensive, so campaigns certainly aspire to put together a spot that voters will remember. If there's one thing that President Dwight D. "Ike" Eisenhower's ad men taught political generations for years to come, it's that rhyming helps. Prior to Eisenhower's presidential bid, he remained nonpartisan and was considered a candidate by both the Republican and Democratic parties. The "I Like Ike" idea was first crafted by Republicans hoping to draft Eisenhower for their presidential bid in 1952. Eisenhower eventually came around to the idea of waging a bid for the presidency on the Republican ticket, and adopted the phrase "I Like Ike" for his campaign.

Watch: 'I Like Ike' Video

Kennedy, Kennedy, Kennedy Not all candidates are lucky enough to have a rhyming nickname. If that fails, however, as the Kennedy campaign demonstrated in 1960, simply repeating the candidate's name over and over again to the tune of a catchy jingle might be enough for voters to take notice. The commercial implies a popular movement behind Kennedy's drive to the White House with supporters of all walks of life -- young and old, white and black -- holding signs and wearing campaign hats bearing the Kennedy name.

Watch: ‘Kennedy, Kennedy, Kennedy’ Video

PHOTOS: JFK As You've Never Seen Him Before

Peace, Little Girl When Lyndon Johnson ran to retain the presidency in 1964, his campaign produced an ad called "Peace, Little Girl," though eventually popularly known as "The Daisy Girl," which might very well hold the distinction of being the most infamous presidential commercial in U.S. history. In the spot, a little girl plucks petals off a flower -- a daisy, of course -- and as she gets closer to one counting down from 10, the ominous voice of a loudspeaker matches her countdown. The camera zooms in on her face before an image of a nuclear blast flashes across the screen. The message of the ad was single: In the Cold War era, with two super powers at a nuclear stand-off, the Republican candidate, Barry Goldwater, would not keep Americans safe. Despite the notoriety of the ad, it actually aired only once, but undoubtedly contributed to Johnson winning the presidency.

Watch: 'Peace, Little Girl'

Morning in America Officially titled "Prouder, Stronger, Better," the campaign ad that would become known as "Morning in America" offered voters with an optimistic take on President Ronald Reagan's first term in office and the promise of four more years of prosperity if reelected. This 1984 campaign ad makes frequent comparisons between economic conditions in 1980 and 1984 and implores voters to consider the impact of returning to those days. Unlike most other campaign ads that are generally remembered for being especially negative, Reagan's uplifting message of optimism for the future of the country -- a message derided at by his opponents of the time -- helped propel him to a second term in office.

Watch: 'It's Morning in America' Video

Willie Horton A convicted felon might seem out of place in a presidential campaign. But in 1988, the campaign of George H.W. Bush used Horton's likeness to great effect in his bid for the presidency against then-Governor of Massachusetts Michael Dukakis. The ad states that Dukakis had allowed a prison furlough program in his state, which permitted prisoners, including convicted murderers like Horton, to spend time away from the cells. During a weekend furlough for which Horton did not return, he committed armed robbery, assault, rape and murder before being captured once again in Maryland. The Dukakis campaign responded with allegations of racism by linking Dukakis to the frightening image of a mug shot of a black criminal. Lee Atwater, a campaign adviser to Bush, even claimed it was his ambition that "people will think Willie Horton is [Dukakis'] running mate." The ad, however, proved successful in framing Dukakis as weak on crime and helped Bush win the White House.

Watch: 'Willie Horton' Video

'Read My Lips' In 1988, then-Vice President George H.W. Bush stood at the podium of the Republican National Convention and proclaimed that if Congress tried to induce him to raise taxes, he could reply: "Read my lips: no new taxes." That pledge helped Bush win the support he needed to become president. However, while in office, the former president had to break his pledge. When 1992 rolled around and Bush faced re-election, the campaign of then-Governor Bill Clinton did not let the country, nor the Bush campaign, forget the pledge he made four years earlier. The repeated use of Bush's pledge in campaign commercials helped convince the public that, even with all the scandals Clinton was facing in the midst of a presidential bid, he and Bush were of similar character, according to polls.

Watch: 'Read My Lips' Attack Ad Video

Swift Boat Facing dwindling support in the polls as a result of an unpopular war, President George W. Bush seemed unlikely to retain office heading into the 2004 presidential election. Although not authorized or produced by the Bush presidential campaign, a series of ads created by the organization "Swift Boat Veterans for Truth" helped Bush's candidacy by attacking his opponent's, Senator John Kerry, major strengths as a candidate: his war record. In the ads, veterans claiming to have served alongside Kerry stated that his military record had been exaggerated and that he lied to earn his medals, including his Purple Hearts and Bronze Star. None of the men who appeared in the ads had actually served with Kerry when he committed the actions earning him those honors. The media blitz became so infamous that "swiftboating" has become a pejorative in American political circles for mudslinging during a campaign.

Watch: 'Swiftboat'’ Video

NEWS: Why Do Negative Presidential Ads Work?

3 A.M. The spiritual successor to Johnson's ad, this spot, known as "3 A.M.," produced by Hillary Clinton's campaign during the 2008 Democratic presidential primaries invokes the same ideas as "Peace, Little Girl," but without the nuclear blast to bring home the point. In the ad, Clinton's campaign presents the idea of a ringing phone in the White House, signalling there's a crisis somewhere in the world even as Americans are sound asleep. Whoever voters want picking up that phone is the one who they should cast their ballots for, according to the ad.

Watch: 'It's 3AM' Video

Rock This entry is more of a personal favorite than a true example of the power of presidential advertising. But even though Mike Gravel, a contender for the 2008 Democratic presidential ticket, never really had a shot at the White House, it was hard to ignore his bizarre ad spots that went viral. In this ad, titled "Rock," Gravel stares straight at the camera for over a minute before walking over to pick up a rock and throw it in the pond in the background. He then ambles away as the address for his website pulls up on the screen. This cryptic ad might not have accomplished anything in terms of boosting Gravel's candidacy, but it one of the many moments that made Gravel an unforgettable part of the last U.S. presidential election.

Watch: 'Rock Throws a Rock' Video

PHOTOS: Un-Presidential Moments in History