Kalu said this on Tuesday while speaking to journalists before the commencement of plenary.
The senate resumed plenary on Tuesday after a seven-week recess.
Speaking on why he is not supporting a presidential candidate from the south-east, the former Abia governor said his decision is based on party affiliation.
“Presidency is not a regional issue. I asked the political parties to zone the presidency to the south-east. When they didn’t do that, and since the presidency is not a regional issue, I had to withdraw,” he said.
“I have no problem with the Igbo man being president, but we have to do it with other Nigerians. If we don’t do it with other Nigerians, it will not work, no matter how popular you are. It’s the president of Nigeria, not the president of Igbo land.
“I’m an Igbo man to the core. I’m also a Nigerian to the core. If anyone from the south-east would have been nominated for the presidency, I would have been the one. So, it’s a party business. I have no grudges against anybody who is running.
“It is not personal. It is political and party-based. This thing is about the party winning elections. I have chosen to be in APC, why will I vote against Tinubu? It’s madness, and I’m not going to do it. Elections go along party line, not along the tribal line.
“But for now, our presidential candidate is Bola Ahmed Tinubu. Tinubu is strategic. He will make his presidency beneficial to the Igbo. The Igbo will be the biggest beneficiaries of Tinubu’s presidency.”