"The camera likes Jacinda. Paul Holmes once said to me 'on TV they see your heart' - she responds well to that so that works really well for her," Mr Key told the AM Show this morning.
"She's been on TV a lot, she communicates pretty well and in the end people want to vote for people they like.
However, Mr Key, who received his knighthood at a ceremony in Government House in Auckland today, does not believer the Ardern effect will be enough to get Labour into power.
"I don't think that will be enough to get [Labour] over the line obviously but I think she'll do substantially better than Andrew Little would have."
Ms Ardern became the leader of the Labour Party on August 1 after Little stepped down, seven weeks before the election on September 23.
