The last minute political fuss over the partial privatisation will put downward pressure on the final price paid for shares in the electricity generator and retailer, but it will not drop below the indicative range set by the Treasury, one source said.
Investment banking sources said it looked like Mighty River would be priced at around $2.35 to $2.45 a share, compared with expectations of $2.60 to $2.80 before the announcement last month of the an alternative power purchasing regime by the Labour and Green parties.
An auction-style book-building process - where institutions put in their indicative bids - will start on Tuesday and a final price will be announced on Wednesday. The stock is expected to list on Friday.
One source close to the transaction said he expected there to be plenty of "price tension" when it came to the book-building process, when institutions put in their bids.
"The Treasury is going to be a in a good position heading into next week," he said. "There is going to be pressure on institutions to bid at the right price," he said.
State-owned Enterprises Minister Tony Ryall said the institutions would play an important role in the process. "While the final decision is made by Ministers, the bookbuild process allows us to determine what value the market puts on the company," he said.
The retail offer has been open for three weeks, and was available only for New Zealanders.
Meanwhile, the Treasury is preparing for the next initial public offers (IPO) for Meridian and Genesis Energy. The Government has said it would like see at least one more IPO this year.