By Vanessa Buschschlüter
BBC News
Panamanians are voting in a general election which has been overshadowed by the disqualification of the man who was leading in the polls.
Ex-President Ricardo Martinelli was the favourite to win until he was banned from running after being found guilty of money laundering.
His replacement on the ballot, José Raúl Mulino, is leading in the polls.
Whoever wins most the votes in this round will be declared president and sworn in on 1 July.
There are a total of eight candidates competing for the presidency, and voters will also choose members of Panama's national assembly.
As presidents cannot serve two consecutive terms, the incumbent, Laurentino "Nito" Cortizo, will not stand for re-election.
Opinion polls put Mr Mulino in the lead. The 64-year-old lawyer from the Realizando Metas (Achieving Goals) party was Mr Martinelli's running mate.
But after Mr Martinelli was sentenced to almost 11 years in prison for money laundering, Mr Mulino joined the race for president.
However, Mr Mulino's candidacy has also faced legal challenges.
Panama's top court was asked to decide whether the fact that Mr Mulino was not chosen by his party in the customary primary election invalidated his candidacy.
On Friday, just two days before the election, the court finally ruled that his candidacy was constitutional.
Mr Mulino has the backing of his former running mate, Ricardo Martinelli, who has been living in the Nicaraguan embassy in Panama City since February, where he was granted political asylum.
From a small room in the embassy, Martinelli has been publishing video messages in support of Mr Mulino, who served as his interior and security minister.
Mr Mulino has said that if elected, he will "close down" the Darién Gap, the dangerous stretch of jungle on Panama's border with Colombia which hundreds of thousands of migrants cross every year on their journey north to the United States.
He has not said how he would close the dangerous route but has made stopping migration an important part of his "law and order" proposals.
A number of recent opinion polls have put Mr Mulino in the lead but with around a fifth of registered voters saying they were still undecided, his rivals are still very much in with a chance.
Two of those hoping to beat Mr Mulino also are very well-known names in Panamanian politics.
Martín Torrijos was president from 2004 to 2009 and is the son of Omar Torrijos, the military ruler who signed a treaty with the US to restore the Panama Canal zone to Panamanian sovereignty in 1977.
The 60-year-old is campaigning under the slogan "Safe Change". He has promised investment in the Panama Canal, one of the main drivers of Panama's economy.
He is standing for the People's Party, which he joined last year after leading the Revolutionary Democratic Party (PRD).
Rómulo Roux, 59, a former president of the Panama Canal's board of directors is running for the national presidency for the second time, after losing to current President Laurentino Cortizo in 2019.
The lawyer, who is standing for the Democratic Change party says that if he elected, he would implement an "aggressive" job creation scheme and improve public services.
He has also said that he would not back the reopening of a controversial copper mine, even though he worked for the law firm which represented the mine.
Another candidate who is trying to reach the presidency for a second time is Ricardo Lombana.
The 49-year-old lawyer ran as an independent in 2019 and is standing for the Other Way Movement this time.
Mr Lombana has dismissed Mr Mulino's promise to "close" the Darién Gap, telling Spanish news agency Efe that "migration, ever since humankind exists, is not stopped by walls".
He instead is proposing to improve security conditions for the migrants who cross Panama on their way north.
Polls will open at 07:00 local time (12:00 GMT) and close nine hours later. Preliminary results are expected to come in soon after the polls close.