Thirteen years is not enough to complete a revolution.

That's the message Venezuelan president Hugo Chávez is taking on the campaign trail as he gears up to fight off perhaps the strongest challenge yet for the presidency he's held since 1999.

Chávez's campaigns are always fiercely contested, accompanied by plenty of bluster and dire warnings about dark US plots. But this time a sagging economy and a unified opposition – not to mention recurring cancer – may make October's vote particularly tense.

Same game, new player

In some ways, this election is shaping up much the way previous challenges to Chávez have. Opposition leaders and the president's supporters are trading warnings about assassination conspiracies and secret coup d'état plans. Government officials warn that "the empire" – the US – will try to exploit any disorder, while opposition lawmakers claim that Chávez is arming loyalist militias. Similar claims and counterclaims were made during the last campaign, six years ago.

But, this time the usually splintered opposition has united around a single candidate, 39-year-old Henrique Capriles Radonski, a political moderate and the governor of one of the country’s most populous states. For the first time, a range of opposition parties co-operated to hold a primary to choose one challenger. Nearly three million people voted in the primary, a heavy turnout that could indicate opposition to Chávez is growing.

Health questions

Chávez is also fighting a persistent cancer. Despite a declaration last year that he'd beaten it, this February he had his third operation, during which a baseball-sized malignant tumour was removed from his pelvic area. He's also completed six rounds of radiotherapy. Never shy to boast, the three-term president recently said: "This cancer can't cope with Chávez." But there's rampant speculation about his health and his ability to assume power for another term.

Add in widespread food shortages, soaring inflation and one of the highest homicide rates in South America, and the conditions could be right for Venezuelans to decide in October it's time to change direction.

Read more: Jon Lee Anderson's insightful 2008 profile of Chávez in the New Yorker magazine.