At a press conference in New Delhi, he cited three previous instances when the prime ministers were chosen post elections.
"We have in the past seen that VP Singh emerged as the prime ministerial candidate only after the elections. In 1996, after the Lok Sabha elections, the United Front was formed and HD Deve Gowda became the prime minister. Similarly, Manmohan Singh was chosen the prime minister during UPA 1 after the elections," he said.
Mr Ali said in a multi-party democracy, the issue of leadership comes after general elections.
"We have to decide by consensus who should be the prime minister," he said.
Expressing confidence that opposition parties will come together, Mr Ali, who was a key player in the formation of the JD(S)-Congress government in Karnataka, said they have realized a multi-cornered contest will not help their cause.
He also said that there cannot be an alternative to the BJP without the Congress being part of a formation of opposition parties.
When his attention was drawn to states where the opposition parties were pitted against each other, he said the "parties can contest each other in those states where there is no threat from the BJP".
On the prospects of the JD(S)-Congress alliance in the 2019 Lok Sabha polls in Karnataka, Mr Ali claimed the alliance will secure "25-plus seats" out of 28 in the state. He said a sub-committee would be formed to come out with a common minimum programme for the polls.
Mr Ali said the ruling alliance in Karnataka will ensure a "stable" government and complete its full five-year term.
To a poser about ministers in Karnataka being upset over portfolio allocation, he said there will be "internal contradictions" but these will be ironed out.
"There is no problem of running the coalition. We have a five-member coordination committee and an AICC general secretary is the member of the committee. It shows the seriousness with which we are taking the coalition," Mr Ali said.
"We have a written agreement where the Congress has accepted that the chief ministership for the JD(S) for five years,"