Editor's note: Julian Zelizer is a professor of history and public affairs at Princeton University and a New America fellow. He is the author of "Jimmy Carter" and the forthcoming book, "The Fierce Urgency of Now: Lyndon Johnson, Congress and the Battle for the Great Society." The opinions expressed in this commentary are solely those of the author.
(CNN) -- In Cedar Rapids, Iowa, independent U.S. Senate candidate Rick Stewart made a bold proposal. He wants to end negative television advertising in the state. Stewart is not the first to call for this. Almost every election cycle, we hear proposals to bring an end to the nasty ads. There is always speculation that we have reached some kind of tipping point.
But in the end, the proposals never go far. The truth is that people hate negative ads, but they pay attention to them. Sometimes, candidates are publicly seen to go too far. Generally, however, the sky is the limit when it comes to negativity.
We've been doing this for a long time. Fifty years ago, Democrats launched a new era in political advertising with the blistering Daisy television spot, a powerful and emotional advertisement that played to the worst fears of the electorate. With images of a young girl picking petals off a flower as a nuclear mushroom cloud is seen in her eyes, Democrats suggested that Republican presidential candidate Barry Goldwater was a right-wing zealot who was capable of starting a nuclear war. Vote for Johnson, Americans were told, or a nuclear holocaust could ensue.
Since that time, campaign professionals have refined and mastered the art of the political spot. On television and radio, and now the Internet, they have developed all sorts of techniques to eviscerate their opponents.
On occasion, they broadcast positive ads trying to introduce themselves to voters. This year was no different.
In states that matter, voters have been bombarded with advertisements meant to frame the choices they face Tuesday.
Here are some of the most memorable ads from this year:
The Catch Your Attention Ad: This goes to Iowa Republican Joni Ernst, who was barely known before she launched an ad boasting of her experience castrating hogs and promising to do the same when she came to Washington. "I grew up castrating hogs on an Iowa farm, so when I get to Washington, I'll know how to cut pork." With a grin on her face and images of pigs on the screen, she says: "Washington's full of big spenders. Let's make 'em squeal."
Ernst catapulted into the national stoplight and emerged as a serious contender for the Senate seat. The ad defined her as someone who was capable of taking on the Washington establishment, and its language jolted the media into giving her substantial coverage. Ernst now leads her Democratic opponent in the polls.
The Bad Taste Ad: The award in this category has to go to Wendy Davis, who, running for governor of Texas, broadcast an ad showing an image of an empty wheelchair. Viewers then heard about the ways that the Republican candidate, Greg Abbott, who is partly paralyzed, has opposed judicial compensation for victims, even though he received $10 million after being severely hurt by a fallen tree.
While the Democrats insisted Davis never wanted to attack Abbott personally, the strategy didn't work well. She was forced to spend more time explaining and justifying than on promoting her message.
The Right to the Point Ad: Sometimes, effective campaign ads are most powerful when they get right to the point, just conveying their main message without any mystery or subtlety. This was the case in Arkansas, when Karl Rove's American Crossroads organization broadcast an ad that tells viewers exactly what they are supposed to take away. The spot shows a spelling bee where a little girl is asked how to spell "Pryor," as in Democratic Sen. Mark Pryor.
She asks the judges for a definition of the word. One of the judges says: "Pryor, a Washington liberal, out of touch with Arkansas, voted with the Obama agenda 90%." Soon after, the girl offers the spelling: "O-B-A-M-A." The judges turn to each other with a smile, saying "close enough," giving her the contest. This is just one of many GOP ads connecting a Democrat from Arkansas to the unpopular president. Similar versions ran in other states.
The Weak on Defense Ad: This has to go to Republicans in Georgia. In 2002, the Georgia GOP used a "weak on defense" ad to boost the chances of Saxby Chambliss against Sen. Max Cleland, a Vietnam veteran who had lost his limbs in the war. With images linking Cleland to Osama bin Laden, the ad informed viewers that Cleland had opposed President Bush's homeland security proposal. Chambliss won the race.
This year, in the race to replace Chambliss, the state has seen more of the same. Republicans ran a misleading ad warning that, according to a leaked campaign memo for the Democratic campaign, Democrat Michelle Nunn ran a nonprofit organization that gave money to organizations linked to terrorism. Even Neil Bush spoke out against the advertisement. His father, former President George H.W. Bush, founded the Points of Light Foundation that she headed. "It really makes my blood boil to think that someone would make that kind of an allegation," Neil Bush said.
The Shoot-Em-Up Ad: Shooting guns has become a popular feature in campaign ads. In certain parts of the country, having your candidate -- Democrat or Republican -- fire off a rifle has become a sign of legitimacy, a signal that they understand the value of gun rights. It's hard to pick the best of the lot since there were many this year. Perhaps the award should go to Kentucky Democrat Alison Lundergan Grimes, shown skeet shooting and explaining: "Mitch McConnell wants you to think I'm Barack Obama. ... I'm not Barack Obama. I disagree with him on guns, coal and the EPA." And "Mitch," she adds, shaking her head, as viewers see an image of McConnell awkwardly holding a gun at an NRA convention, "that's not how you hold a gun."
The Soft on Crime Card: There have been a number of ads tapping into the sentiment of 1988 when a group supporting George H.W. Bush's campaign ran a racially loaded ad about a convict who had been let out for a weekend furlough in Massachusetts and raped a woman while he was free. This year, Democrat Mark Begich took a page from that strategy suggesting that while he was the state's attorney general, his Republican opponent Dan Sullivan had responsibility for a sex offender who had been let out of prison and went on to commit murder and a sexual assault.
The ad has a police officer contending that Sullivan set many sex offenders free. "One of them got out of prison and is now charged with breaking into that apartment building, murdering a senior couple and sexually assaulting their 2-year-old granddaughter." Sullivan released a statement saying that "He is lying to Alaskans and using the murder of an elderly couple and the sexual assault of a 2-year-old for his own political gain, and it's despicable."
Begich was forced to pull the ad, and he has encountered intense criticism for running it. Sullivan's team expressed its opposition through an ad called "Shameful." The attorney for the family asked both campaigns to take the ads off for fear they would affect the jury pool in the trial.
These are just a few of the ads that took the spotlight this year. Soon the spots will go dark. But with the 2016 presidential race around the corner, voters can expect to see a big new crop of ads, many of them negative, as we get closer to that election.
(Note: An earlier version of this article said the George H.W. Bush campaign aired the Willie Horton ad; it was a group supporting the campaign that aired it.)