No Tour de France competition is as hard to predict as the battle for the polka-dot jersey of best climber. While it has mostly been won by aggressive opportunists, a recent rule change has also made the tunic a viable goal for the GC contenders. Many riders start the race with an eye on the coveted jersey but the battle is further complicated by the facts that luck plays a crucial role and that many riders end up as jersey contenders almost by pure accident.

 The list of winners of the polka-dot jersey is a prestigious one and contains many of the best pure climbers, the sport of cycling has ever seen. Hence, it was painful for Tour organizers to see the lesser known Anthony Charteau ride into Paris in the famous tunic at the end of the 2010 edition of the race.

To avoid a similar scenario, they introduced what has been referred to as a "Lex Charteau": a rule change that should make the real mountains more important than the smaller climbs and that would give points to fewer riders on each climb. The purpose was clear: ASO wanted a "big" rider and a real climber to win the jersey.

The effect of the rule change was immediate: in 2011, it was GC rider Samuel Sanchez who rode into Paris in the polka-dot jersey. Last year, the jersey was once again taken by an opportunist but ASO were probably not unhappy to see local hero Thomas Voeckler bring home the coveted tunic. After all, the Frenchman had finished 4th overall one year earlier and so should be regarded as a "big" rider also by ASO.

This year, the battle once again shapes up to be a close one which could be won either by an opportunist or a GC rider. Luck plays a crucial role in the mountains competition as it is important to hit the breakaway in the decisive stages where there are many points at stake. Hence, many riders start the race with an eye on the classification but without making the jersey their only target in the race. After the first couple of mountain stages, a handful of riders find themselves in contention and they are often set to fight it out between them throughout the rest of the race.

It is much harder to predict the winner of the polka-dot jersey than it is to pick out potential victors in the battle for the other distinct tunics. Nonetheless, Voeckler once again marks himself out as the man to beat.

The Europcar rider has been very vague on his Tour targets, only stating that Pierre Rolland is the team's GC rider and that he has a free role himself. That role will probably see him chase a stage win in the mountains but he is very likely to also keep an eye on the KOM standings.

Voeckler is in splendid condition at the moment, having recently won a hard stage at the Dauphiné and the Pyrenean Route du Sud overall. During recent years, he has developed from a classic opportunist who excelled in hilly terrain, into much more of a climber. What makes him a danger man in the competition is his formidable ability to get into the crucial breaks - this year stages 9 and 19 appear to be decisive if an opportunist is to win the jersey - and his fast sprint that usually allows him to pick up maximum points on the climbs.

Euskaltel is the only team to have officially made the jersey an objective and with climbers Igor Anton and Mikel Nieve in the line-up, the team has two very good candidates. While they will probably keep an eye on the GC, both are most likely to go for a big stage win in the mountains and that could very well place them at the pointy end of the mountains classification as well. Anton is probably the better climber of the two while Nieve has made wins from epic long-distance breakaways his specialty. However, both are disadvantaged by their lack of punch and will have no chance against Voeckler in a sprint.

Damiano Cunego and Daniel Martin both start the race with the GC as their clear objective but they are unlikely to make an impression among the best. If they fall out of contention, they are likely to start chasing a stage win in the mountains and that could also put them into the battle for the mountains jersey. Robert Gesink is at the race mostly to support Bauke Mollema but also targets a stage win on one of the hardest days and could also mix it up in the fight for the polka-dots if he suddenly finds himself up there. His teammate Laurens Ten Dam, French climbers Brice Feillu and John Gadret, newly-crowned Dutch champion Johnny Hoogerland and last year's runner-up Frederik Kessiakoff are other opportunists that could make a win in the competition an objective during the race.

Last year, the race favourites contested the stage win in only one of the mountain stages as Chris Froome won on La Planche Des Belle Filles. Of course that played into the attackers' hand and the highest-placed GC rider in the mountains classification was Pierre Rolland in 4th (and he had even picked up most of his points during a breakaway in the Alps).

This year the number of potential stage winners among the favourites is much bigger which makes it likely that more stages will be played out among the GC riders. At the same time, the stages to Mont Ventoux and Alpe d'Huez are highly prestigious and so breakaways won't have many chances on those two days.

This means that the GC riders should have  a better chance than they had last year. Chris Froome will not make the jersey a target and never start to pick up points deliberately but he could very well turn out as the strongest climber in the race. He would love to win on both the Mont Ventoux and the Alpe d'Huez and that alone would make him a danger man in the mountains classification.

When Sanchez won in 2011, he did so by virtue of a stage win that suddenly put him into the polka-dot jersey. From then on, he started to chase points. We could see a similar scenario this year that could put riders like Nairo Quintana, Pierre Rolland, Joaquin Rodriguez, Alejandro Valverde and Thibaut Pinot into the mix. They are unlikely to make it their most important objective but the jersey could be an added bonus that follows from successful stages in the mountains.

The favourites:

*** Thomas Voeckler

** Igor Anton, Mikel Nieve

* Chris Froome