"Now, there is an awful lot of National supporters I think who would say, 'I don't want a far left-wing Government that the Greens and Labour represent', so as he [Mr Craig] himself said these things are all about give and take and compromise. That's the nature of government.
"But my expectations are that we will have discussions with Colin Craig at some point, as indeed we will with hopefully a number of other parties."
Mr Key said his party had "lots of choices available to it" when it came to possible coalition partners.
He was speaking after a recent 3News poll showed National on 46.3 per cent would get 60 seats in Parliament, which is not enough to govern alone. The Conservatives, on 2.7 per cent, would add four seats, and hand Mr Key a clear majority if they were to partner.
However, Mr Key wouldn't go into details about how such a deal would work or what issues he was willing to compromise on to retain his position as Prime Minister for another term.
"I haven't had those discussions today and I wouldn't, certainly, be conducting those through the media," he told 3News this morning.
The show's poll showed only a third of voters would support a deal with the Conservatives.
Mr Key admitted that "some people will be concerned about his [Mr Craig's] moral issues" but said he would reassure people that such matters come down to conscience votes in Parliament.
Mr Craig has already said he would try to overturn the anti-smacking law if he were to secure a seat at the Beehive. He is also against gay marriage, is sceptical of Treaty claims and man-made climate change.
"The fact we've different views on those things doesn't really matter because they're ultimately a conscience vote," Mr Key said.
"So if he wanted to push those issues and was a member of parliament he'd have to get 61 members of Parliament, presumably across the Parliament, to vote for that, and that as we know wouldn't be easy."
