A presidential election in North America in which there are no negative campaign ads?
Believe it or not, it is unfolding right now in Mexico – a stark contrast to the U.S. Republican leadership race I have been following in which negative TV ads have had a defining role. The rest of the U.S. election cycle will be no different. In Canada, the recently-minted leader of the official opposition will likely soon feel the brunt of Tory attack ads.
But in Mexico, the political battle over the country's direction and issues relating to security – 50,000 have been killed in drug war violence in the last five years – will have to take place under a unique and new set of campaign rules that ban negative political advertising.
The decision followed a deeply contentious 2006 contest.
In that presidential election, half a per cent – or about 250,000 votes – separated the winner Felipe Calderón and runner-up Andres Manuel Lopez Obrador.
In a close race, negative ads that introduced the spectre of a candidate resembling Venezuelan President Hugo Chávez winning the election were seen as innuendo meant to damage Mr. Obrador's candidacy.
"There was the idea that, by the close association, do we want another Chávez? It's dangerous; the guy's an extremist; he's a mad man. All of those sort of ideas were floating around and obviously hurt Lopez Obrador," explains Professor Peter M. Ward, an expert in Mexican politics and U.S.-Mexico relations at the University of Texas at Austin.
"The complaint was very much that these negative ads had essentially cost him the election. And in part that is probably true."
This time around, Mexico's federal electoral institute is closely monitoring broadcast ads and will likely ask campaigns to remove ads that break rules put in place in 2007.
Campaigns may also be asked to apologize and pay fines for running negative ads, adds Professor Ward.
There is a blind spot, however.
"In my conversations with folks at the electoral tribunal in Mexico, they acknowledge there is no way they can control social media. You're going to see a lot of stuff, a lot of little video clips on YouTube. This is already happening," Professor Ward believes.
Changes to the rules also mean that the campaign season is exactly three months long, culminating in the July 1st vote in which Mexicans will choose a successor to President Calderón, who is barred by the constitution from seeking a second six-year term.
Two of the three presidential candidates kicked off their three-month sprint to voting day exactly one minute after midnight on March 30th, careful not to break new campaign rules. New rules also limit TV ad spending.
But by far the biggest change in Mexican electoral law is the move away from negative TV ads.
A similar move in the U.S. politics is almost impossible to imagine.
With seven month to go before the November U.S. presidential election, the contest between President Barack Obama and the eventual Republican nominee – presumed to be Mitt Romney – will be defined by an onslaught of TV attack ads intended to influence swing voters.
The template is the Republican leadership race.
The Romney campaign has spent nearly $12-million on TV ads, the vast majority of them positive. However, friends and allies of Mr. Romney have used the Restore our Future Super PAC to outspend their Republican rivals in every primary contest.
According the Center for Responsive Politics, the pro-Romney Super PAC has spent $35-million in negative TV ads against Rick Santorum and Newt Gingrich. How much has the group spent promoting its candidate? $1.1-million.
Negative ads are often most effective when there is a 'volatile' electorate, or a high number of undecided voters. In Mexico, presidential contests take volatility to another level.
"You have to remember that in Mexico it's something like 40 per cent of the electorate is up for grabs... And that's what makes elections so interesting in Mexico frankly," according to Professor Ward, who lives in Austin, Texas.
Does the prospect of a presidential election without any negative ads sound like a breath of fresh air?
"No, quite the opposite," says Professor Ward, adding that although he does not believe in "gratuitous" attack ads there is the threat of creating an "artificially sanitized" presidential contest.
"I'm not in favour of something that really is so restrictive that it impedes debate and impedes scrutiny of individuals. I think that's the real danger here," he explains.
Josefina Vasquez Mota, the first woman candidate for a major political party, could make history as Mexico's first-ever woman president. She is representing the ruling National Action Party (PAN), which has held power since 2000.
Ms. Mota currently trails the front-runner Enrique Pena Nieto of the Institutional Revolutionary Party (PRI) by 18 percentage points in the latest poll, although she is polling ahead of Mr. Obrador.
In another election campaign, a few sharp and negative attack ads could dramatically narrow the race. This time, however, it will be a lot more difficult to catch a front-runner.