The Greens have expressed concerns about O'Connor's comments in his previous role as Police Association president, where he was an advocate for arming police and taking a tougher stance on drugs.
Shaw said the party was now willing to put those differences aside.
"Greg has said things in the past that progressive voters would take issue with.
"I would suggest that people question him about those statements. They've got to decide for themselves whether they're satisfied with the answers to those questions.
"But my view is that the greater priority is to change the Government."
Labour and Greens last month said they had agreed not to cut "deals" in marginal seats as part of their Memorandum of Understanding.
Shaw said the Green's decision not to run in Ohariu was made by his party alone and was not part of a formal arrangement with Labour.
Dunne has held the seat since 1984 and his party has been a support partner for National since 2008.