Mr Goldsmith is toeing the party line by campaigning only for the party vote, which infuriates Mr Lange.
"I just want to frog-march this guy [Goldsmith] across the line," Mr Lange said.
He has created three posters with a humorous message to "Vote Goldsmith" , but chickened out of distributing them when faced with the possibility of being fined for breaching an electoral law that says posters must be officially authorised.
Mr Lange said his unofficial campaign was an attempt to "put Act out of its own misery".
If not, he hoped the loophole that allowed this "coat-tailing" to occur would be addressed by a possible review of the MMP voting system before the 2014 elections.
"My dream is by the next election we will have a free and fair and open election."
It is not the first time the left-leaning Mr Lange has held his nose and voted for a National candidate in Epsom. He voted for Richard Worth at the last elections when Mr Key did a similar deal to get Act's Rodney Hide into Parliament.
"It was a horrible experience ... I could hear my father and grandfather turning in their graves."