Asked to expand on his initial response, he said: "Well I'll leave you to interpret it. I don't think it's likely he'll win."
Mr Key ruled out any return of Mr Gilmore to National's caucus, but said he believed that if Mr Gilmore were to stand it would be as an independent.
When APNZ asked Mr Gilmore if he planned to stand, he refused to answer. "I'm not saying anything. The media are all liars.
"You all nearly killed my mother," he said.
Mr Gilmore argued in his blog post that the Christchurch East seat was not a safe seat for Labour, after a loss of 12,000 voters since the earthquakes and new housing developments.
He said the population shift meant many people were now in Parklands instead of Aranui.
National won 13,252 party votes in the seat in 2011, compared to 9100 for Labour.
Lianne Dalziel won the seat by a 5334 majority in 2011.
Mr Gilmore hoped Labour would choose someone young and local to win the seat.
Ngai Tahu manager James Caygill and sitting list MP Clayton Cosgrove are seen as key runners for Labour.
Mr Caygill told media yesterday he would seek the nomination.
Mr Gilmore resigned as an MP last month after he verbally abused a waiter at a Hanmer Springs hotel for refusing to serve his dining party more wine.