The main opposition candidate in Venezuela, Manuel Rosales, has registered his candidacy for December's presidential election.
Thousands marched in support of Mr Rosales in Caracas
He led thousands of his supporters on a march through Caracas to the headquarters of the electoral council to formalise his candidacy.
Mr Rosales is the governor of the oil-rich Zulia state in west Venezuela.
The Venezuelan opposition has proclaimed him its sole candidate to stand against President Hugo Chavez.
For many in the opposition in Venezuela, Mr Rosales represents their only realistic hope of seeing President Hugo Chavez removed from office anytime soon.
Promise of change
Addressing thousands of his supporters outside the National Electoral Council in Caracas, the 54-year-old state governor dared them to imagine another kind of Venezuela.
Mr Rosales faces a tough campaign
It was possible to bring about change, he said, if people came out and fought for a modern society.
He said he represented neither US imperialism nor support for "the bearded one", a reference to President Chavez's close ally, Fidel Castro of Cuba.
The opposition in Venezuela, so often fractured and discordant, is making a concerted effort to unite.
Earlier this month, the other main opposition candidates stepped aside to allow Mr Rosales to be crowned their "sole candidate".
There are still a number of independent candidates in the race.
But opponents of President Chavez see in Mr Rosales something they have lacked for some time: a clear leader around whom they can mobilise their efforts.
Nevertheless, he faces a difficult campaign.
Opinion polls suggest that President Chavez has an unassailable lead.
It is also unclear whether Mr Rosales can transfer his local popularity in the state of Zulia, where he has been governor for over 10 years, to the national stage.
And some analysts say his policies - which include using the country's oil-wealth to set up a debit card system of state benefits for the poor - are reminiscent of the populist style of President Chavez, precisely the kind of politics that many of his opponents say they are trying to get away from.