(CNN) -- Singing folk songs and strumming the guitar at his campaign rallies, Hugo Chavez shows no sign that he's facing the strongest challenge to his 13-year rule in Venezuela. He has dismissed his much younger challenger, Henrique Capriles Radonski, as a "fly" not worth chasing, when challenged to a debate earlier this year. Chavez's opponents are confident that this Sunday, Capriles will unseat the long-ruling leftist leader, a refrain previously heard before eventual defeats. Yet the incumbent is a political survivor and remains popular at home. But there are signals, observers say, that this time Chavez really is on the ropes.
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On Sunday, Venezuelans will vote for president
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Longtime leader Hugo Chavez is vying for a fourth term
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His challenger is 40-year-old Henrique Capriles Radonski
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Observers have expressed concern about post-election instability
Henrique Capriles Radonski
Capriles
Henrique Capriles Radonski
Those supporting @placeholder say people were afraid to voice their real opinions.
Hugo Chavez
Chavez
Chavez
Hugo Chavez
The image makeover is part of an effort to capture support for @placeholder among Venezuela's undecided voters -- mostly young people -- who make up 23% of the electorate and could play a pivotal role in Sunday's election.
Henrique Capriles Radonski
Capriles
Henrique Capriles Radonski
"Venezuelans are looking for a new way," @placeholder has told his supporters.
Hugo Chavez
Chavez
Chavez
Hugo Chavez
Whatever his health condition, @placeholder remains a force in Venezuelan politics.
Henrique Capriles Radonski
Capriles
Henrique Capriles Radonski
However, @placeholder has been constantly on the road, and his supporters say the momentum is shifting.
Henrique Capriles Radonski
Capriles
Henrique Capriles Radonski
Chavez's campaign said the money purportedly was a bribe for his opponents campaign and accused the @placeholder camp of financing itself in this way.
Hugo Chavez
Chavez
Chavez
Hugo Chavez
Representatives from @placeholder's campaign declined to comment, but Chavez told reporters last week that a Capriles victory was impossible, citing polls.