Is it in behalf of or on behalf of?

The Merriam-Webster online dictionary has the following:

A body of opinion favors in with the “interest, benefit” sense of behalf and on with the “support, defense” sense. This distinction has been observed by some writers but overall has never had a sound basis in actual usage. In current British use, on behalf (of) has replaced in behalf (of); both are still used in American English, but the distinction is frequently not observed.

in behalf of means for the benefit of
The letter was written in behalf of a colleague
The money was collected in behalf of hurricane victims.

on behalf of means as the agent of
The lawyer acted on behalf of her client.
The producer accepted the award on behalf of the cast.