U.S. Sen. Sheldon Whitehouse can cross one name off his list of potential opponents: Cranston Mayor Allan Fung, who thinks Republicans will need to spend $5 million to be competitive against the first-term Democrat.

“I’m not considering a run against Sheldon in 2012,” Fung told my colleague Tim White this morning.

When Tim first broached the idea with him, Fung replied: “Unless the national Republican Party plunks down $5 million…” before letting out a laugh. “It’s going to be a very expensive race,” he said.

Fung also told Tim he’s “planning” on seeking a third term as mayor next year; he previously won in 2008 and 2010. Fung was a city councilman and a lawyer for MetLife before becoming mayor.

Fung won’t lack for funds if he does run for mayor – or any other office in the state, for that matter. His $75,000 campaign war chest is the fifth-largest among Rhode Island’s top politicians, a WPRI.com survey found earlier this month.

Fung’s fellow Republican mayor, Warwick’s Scott Avedisian, told me yesterday he is thinking about entering the race against Whitehouse, and suggested a G.O.P. candidate would need to throw his hat into the ring by June if he wants to mount a competitive bid.

Avedisian’s war chest was sixth-biggest in the state – right behind Fung’s – in our WPRI.com survey, at $71,000. But he couldn’t use that money for a Senate race since it’s a federal office.

In the meantime, all eyes are on Florida’s Hutchinson Island, where former Gov. Don Carcieri has a vacation home – and is weighing whether to jump into the race. And then, of course, there’s always the possibility of a dark-horse candidate coming out of left field – just as Carcieri himself did back in 2002.