A ranking KNP official said the decision was made during the coalitions executive committee meeting on Tuesday, where party representatives also agreed to finalize their list of local candidates by next week.
"This is some kind of deadline because its not enough that they (national and local political leaders) tell us privately that they are supporting FPJ yet they cannot come out in the open," the KNP leader said.
He said that a declaration of support would help boost Poes candidacy and compensate for the lack of local KNP candidates in many areas.
The KNP was reportedly able to field candidates in only about half of the total number of local posts up for grabs in the May 10 elections.
KNP officials said they were resorting to forging local alliances with anti-administration bets to compensate for the lack of candidates.
Earlier, some 15 congressmen and incumbent local officials from the administration Lakas-Christian Muslim Democrats, the Nationalist Peoples Coalition and the Liberal Party declared their support for Poes candidacy.
Poes spokesman Rep. Francis Escudero sees April 15 as less a "deadline" than an invitation for their silent allies to declare their support early.
"Politics is addition so it doesnt mean were not going to accept allies from April 16 onwards," he said. "The earlier, the better."
But Escudero is keeping mum on whether independent presidential candidate Sen. Panfilo Lacson would be among these latecomers to the KNP fold.
He explained that only Poe and Lacson would know of any possible unification talks at the presidential level.
"I wont even dare comment on the issue this time. Personally, I know I cant speak for him (Poe) on this matter," he said.
Both the KNP and Lacson insist that a united opposition will be possible only if one of the two presidential contenders would give way.
The other day Lacson said he was still open to unification talks with Poe only if the movie actor agreed to be his vice president.
This appears to be an impossible condition as Poe, who is in a virtual tie with President Arroyo in the latest voters survey, is unlikely to back out of the race.
Meanwhile, KNP senatorial candidate Salvador Escudero III blamed rumors of "junking" within their ranks to the "collegial" nature of this years Senate race.
"The suspicion is already built in the collegial nature of the elections," Escudero said.
Escudero explained that any misgivings within a political coalition are understandable when it is a mixed group.
To illustrate his point, Escudero cited the presence of former hard-hitting opposition members like Miriam Defensor Santiago and Sen. John Osmeña in the administration K-4 (Koalisyon ng Katapatan at Karanasan sa Kinabukasan) coalition and the presence in the KNP of figures formerly identified with the administration like Sen. Aquilino Pimentel, Ernesto Herrera and Alfredo Lim.
"Only the C and D classes are known for straight voting. The A and B classes would choose from different parties and often not even complete the slate," he said.
Asked if the KNP bets would confront fellow candidate Francisco Tatad, Escudero replied: "Hindi na aabot sa ganun (It wont come to that)."
Tatad has been identified as the one who complained about the alleged junking of candidates.
Other KNP senate candidates like Pimentel, Boots Anson-Roa and Mindanao Rep. Didagen Dilangalen have denied the existence of any junking.