But that decision could be little more than a formality with the public authorities -- 21 government representatives who sit on the WADA Executive Committee and Foundation board -- preparing to pick their preferred candidate on Tuesday.
The public authorities will meet in Montreal ahead of WADA's Executive Committee and Foundation board meetings on Wednesday and Thursday when they are expected to make their choice between the two former elite athletes.
Five continental regions could each nominate a candidate for the top anti-doping job but only two entered the race with Europe putting forward Banka and the Americas Diaz.
Outspoken WADA vice-president Linda Helleland, who was critical of the Executive Committee's controversial decision last September to reinstate the Russian Anti-Doping Agency (RUSADA), was once viewed as a leading contender only to have the Council of Europe back Banka.
The former Norwegian minister could yet be a factor in the outcome if she can secure the backing of a least one Foundation board member and submits her candidacy to WADA before a May 31 deadline.
All indications are, however, that the next president will be Diaz or Banka, both former athletes, government officials and WADA Executive Committee members.
Banka, the 34-year-old minister of Sport and Tourism who helped Poland to a bronze medal in the 4x400 metres relay at the 2007 world championships, would bring some youthful energy to a post where the three previous presidents -- Dick Pound, John Fahey and Reedie -- were well into their 60s when at the helm.
The 44-year-old Diaz, a long distance swimmer inducted into the International Marathon Swimming Hall of Fame and vice-minister of Sport and Tourism in the Dominican Republic, combines enthusiasm with plenty of experience sitting on both the WADA Executive Committee and Foundation board.
TROUBLED AGENCY
Whoever emerges as the next WADA president will take over an agency in turmoil.
WADA's handling of the Russian scandal fractured the anti-doping movement, with many athletes having lost faith in the organisation and the process put in place to protect them.
RUSADA was suspended in 2015 after a WADA-commissioned report by Canadian lawyer Dick Pound outlined evidence of state-backed, systematic doping in Russian athletics.
The Russian agency's reinstatement last year angered a string of sports bodies and athletes around the world.
As WADA emerges from the scandal deep divisions remain.
Restoring confidence and trust will be the first job for the new WADA chief.
Diaz and Banka have campaigned on the idea that athletes need to be part of the decision-making process at every level.
But both men, against the urging of many athletes groups, voted to reinstate Russia before RUSADA had met all its obligations in the Roadmap to Compliance.
"I will always think as an athlete and when athletes don't have the information, we are not capable of bringing our criticism to the place where decisions are made and we feel frustrated," Diaz told Reuters in a phone interview from the Dominican Republic. "When criticism happens you need to hear."
Banka was not available for an interview but in an email he outlined his platform, including the need for an athletes’ commission within every national anti-doping organisation.
"Athletes should be engaged in anti-doping activities, including the decision-making processes," wrote Banka. "One of the major weaknesses of WADA, exposed by the Russian crisis, was a lack of communication, especially with athletes."
Banka would also like to see a fund to build testing laboratories, while Diaz wants more diversity within WADA's ranks and highlights the critical need to develop resources, noting that a Major League Baseball player's yearly salary is in some cases as much as the agency's entire operating budget.
"If we are regulating sport, a trillion dollar industry, close to $40 million a year is not enough, especially compared to the salary of one Major League Baseball player," said Diaz.
"I think definitely we're in a moment in which I personally believe we're going to be capable of defending the WADA everyone demands -- a closer (together) WADA with greater reach."
(Editing by Ken Ferris)
