This was confirmed by the younger Estrada, who spoke with a group of police officers moments before father and son cast their ballots at the presidential suite of the Veterans Memorial Medical Center (VMMC) in Quezon City.
"Hindi namin iboboto si Mercado (We wont vote for Mercado)," one police officer quoted the San Juan mayor as saying.
Over coffee, the younger Estrada told the policemen he was extremely disappointed with Mercado for having abandoned his father at a time when he was needed most.
Mercado is seeking to return to the Senate as an independent candidate. He was invited as a guest candidate in the 13-man senatorial ticket of Estradas Puwersa ng Masa.
Sources said Estrada was still bitter over Mercados participation in People Power II, which forced the former First Family to leave Malacañang last Jan. 20.
The former defense secretary had also been quiet during the period leading to Estradas arrest and in the aftermath of the Labor Day riots in Mendiola.
Earlier, Estradas lawyer Raymund Fortun said the former president would be voting a straight opposition ticket.
While junking Mercado, the younger Estrada urged those present in the hospital room to vote for his mother, Puwersa senatorial bet and former First Lady Luisa Ejercito.
The San Juan mayor was awake as early as 6:30 a.m., welcoming policemen and Commission on Elections (Comelec) officers who brought ballot boxes for the detainees.
The Estradas were airlifted to the VMMC the other day after both fell sick while under detention in a bungalow-type jail at Fort Sto. Domingo in Sta. Rosa, Laguna.
The Sandiganbayan ruled earlier that the two high-profile inmates should be allowed to cast their votes in the precincts where they were registered in compliance with the law.
However, the Department of the Interior and Local Government and the Philippine National Police (PNP) filed a joint petition asking the anti-graft court to reconsider its decision for security reasons.
The sprawling VMMC, which comes complete with a golf course, had been turned into something resembling a heavily guarded military base as officials wanted to ensure that the deposed leader is neither attacked by enemies nor freed by supporters.
Police stood guard outside the hospital compound, while Army troops set up hammocks in the inside lawn.
Officials refused to give numbers for the security detachment, but up to seven police officers were seen searching cars that entered the compound and two armored personnel carriers were in place.
Mediamen gathered at the VMMC gates as early as 5:45 a.m. were prevented from entering the premises.
Comelec National Capital Region director Rafael Rafanan was on hand to supervise the special electoral proceedings.
The Comelec team came with election paraphernalia that included the requisite ballots, voters registration records of the detainees and two ballot boxes marked 268-A and 448-A.
Estrada is a registered voter at precinct 268-A of the Pedro Cruz Elementary School in San Juan while his son is registered at a precinct in Barangay Greenhills.
The former president was up at around 7:10 a.m. but decided to wait for one of his lawyers before casting his ballot. Lawyer Jose Flaminiano arrived shortly after 8 a.m.
San Juan police chief Superintendent Rodrigo de Gracia, who was part of the security force, told reporters that the voting was also delayed because the former leader had made certain demands.
Estrada reportedly wanted full coverage over Net 25 television and dzEC radio before he and his son would cast their ballots.
At 9:10 a.m. father and son started filling out their ballots and had their votes locked up in gold-colored ballot boxes. The whole process lasted some 15 minutes.
Among Estradas early visitors was close friend and fellow-movie actor Fernando Poe Jr. Visitors, however, had to pass through a series of security checks before being allowed inside the receiving area.
The PNP said there had been no immediate indications of security problems at the VMMC.
Meanwhile, Doctors Salvador Flores and Liberato Casison, Estradas attending physicians at the VMMC, said the condition of the former president was improving.
The ousted president complained of difficulty in breathing and severe pain in his legs because of arthritis. He was diagnosed as suffering from bronchitis and nursing a slight fever. His son also complained of abdominal pains.
Doctors have scheduled further testing on both patients. With Cecille Suerte Felipe, Mayen Jaymalin