A long-serving National Party official says there is no doubt the party's leader will publicly back the ACT Party's candidate in Epsom.
Speculation is growing about the likelihood and timing of John Key having a symbolic cup of tea with ACT candidate John Banks - a nod to National supporters to give their electorate vote to Mr Banks.
ACT probably needs to win the Epsom seat in order to return to Parliament and partner again with National.
National's former party president, John Slater, is sure the endorsement will occur due to the need to retain partners in the MMP voting system.
Despite changes in ACT since the last election, Mr Slater believes National supporters in Epsom will not change their commitment to strategic voting.
"I think people realise in an electorate like Epsom, it's similar to Ohariu and others where it's quite tactically needed to get coalition partners through."
National's Paul Goldsmith is seeking only the party vote - but two recent polls have put him ahead of John Banks as a candidate.
At the latest candidates debate in the electorate, on Wednesday, Mr Goldsmith said he wanted to get into Parliament, and to represent the people of Epsom in Parliament, but said he was "relaxed about how that happens."
Mr Banks says while not pursuing an endorsement, getting one would be a blessing.
He says three years ago, the cup of tea between Mr Key and ACT's candidate at the time, Rodney Hide, occurred on the Sunday before polling day.