"This is not an insignificant issue. The majority of people genuinely feel their MP should be guided by their own electorate and not their own opinion."
Mr Craig said that if he was elected, he would vote for gay marriage if his electorate demanded it, in spite of his strong opposition to the law change.
The Conservative leader said Mr Key was "a perfect example of how things are going wrong".
The Prime Minister had previously voted against civil unions and the Prostitution Reform Act.
Helensville voters had been highly influential in Mr Key's last-ditch decision to oppose the prostitution law change, after backing it at the first and second readings.
The leaflet includes a survey of 2200 New Zealanders commissioned by Mr Craig which showed that 71 per cent of respondents felt MPs should consult their electorates and vote according to their wishes.
Last year, Mr Craig distributed 20,000 pamphlets in Helensville which said that Mr Key was "too gay" to represent what Mr Craig felt was a conservative-minded electorate.
He also spent $1.6 million on his party's runup to the 2011 election, in which the Conservatives polled 2.6 per cent and gained no seats.
Asked whether his personal wealth gave him a significant advantage over MPs, Mr Craig said: "We don't have any parliamentary funding so we start right behind the game."
He added: "It does cost money to be in politics, and it's helpful that I've got an income. But having said that, it wouldn't be possible if we didn't have such a base of volunteers."
MPs are not permitted to use Parliamentary Services funding to solicit votes or members for their party.
The Conservative Party's survey, which had a margin of error of 5 per cent, also found that a third of respondents did not know the same-sex marriage bill would also permit gay couples to adopt children. At present, gay individuals but not gay couples are able to adopt.
Mr Craig felt that if it was widely known that adoption laws would be altered by the bill, public opposition to it would grow.
"It's one thing to be talking about what two people do in the privacy of their own home. It's another thing when that becomes a discussion about parenting kids who need a family.
"From looking at the debate overseas, that is one of the things that makes people more conservative rather than liberal on this issue."