SACRAMENTO — It’s being billed as a battle of the whales here in the state capital, an increasingly fierce contest pitting billionaire against billionaire. The prize is not California’s governorship or the fate of some ballot proposal, but ownership of the N.B.A.’s most troubled franchise, the Sacramento Kings.

A group from Seattle, trying to redeem the loss of its beloved SuperSonics in 2008, struck first. Led by Christopher Hansen, a hedge fund manager, and backed by Steven A. Ballmer, Microsoft’s chief executive, the group of investors announced last month that it planned to buy the team, move it to Seattle by next season and rename it the SuperSonics.

Since then, Sacramento’s mayor, Kevin Johnson, who happens to be a former National Basketball Association star, and his allies have been scrambling to put together a counteroffer to keep the team here. They say that Sacramento will announce its proposal, backed by California investors, before the end of this month.

In an interview, Mayor Johnson said that many wealthy Californians expressed an interest in saving the Kings, but that he has pursued conversations with those capable of ponying up the $1 billion necessary to buy the team and build a new arena in downtown Sacramento.