Bolivia's May 3 general election campaign officially began on Monday as the deadline for presidential and legislative candidates to register passed, with exiled former president Evo Morales seeking a legislative seat.
Morales, who resigned in November after almost 14 years leading the landlocked South American country, is barred from standing for president.
But on Monday, he officially registered as a candidate for the senate representing the Cochabamba region in Bolivia's south, the supreme electoral court (TSE) said on its website.
The results of the October 20 election were annulled after an audit by the Organization of American States found evidence of vote-rigging in Morales's favor.
That revelation led to the military's withdrawing support for the former trade unionist. He resigned on November 10 after three weeks of protests against the election result by opponents who accused Morales of fraud.
"As of now candidates and political alliances can start to approach the citizenry and win more support," said TSE president Salvador Romero.
All six previous TSE magistrates were detained following the October election, accused of rigging the results.
Morales took to Twitter on Monday to denounce the interim government for allegedly trying to apprehend his lawyer Wilfredo Chavez as he sought to register the ex-president as a legislative candidate.
Morales was Bolivia's first indigenous president but since his exile has been accused by the interim government of sedition and terrorism for allegedly urging his supporters to lay siege to major cities including La Paz.
Besides Arce, seven other presidential candidates have registered, including conservative interim leader Jeanine Áñez. She initially had insisted she would not stand and was running fourth in the last opinion poll with 12 percent.
Centrist former president Carlos Mesa, beaten by Morales in the October vote, is standing again.
Just as in the last election in October, opponents to Morales have failed to form a united front despite meeting on Saturday in a bid to do so. They are in a "narcissism contest" according to Waldo Albarracin, dean at San Andres University, one of the most important in Bolivia.
United Nations envoy Jean Arnault called the start of campaigning "a decisive stage of the electoral process and consolidation of peace in Bolivia."
In the first round of voting, a candidate needs to win an absolute majority or gain at least 40 percent with a minimum 10-point lead over the nearest challenger.