The Sacramento Kings may be headed for the exit, but their threatened departure has energized the effort to build a new sports arena.

A grass-roots campaign emerged Wednesday to raise money for a new facility in Sacramento. Within hours, the movement spread through social media and billboards along area freeways.

At the same time, Sacramento city leaders vowed to press ahead with their years-long, frequently frustrating effort to find an arena financing plan that works. A city-sponsored development team continues to analyze the economics of a new building, with a report expected in late May.

"Our community realizes we need to build a new entertainment and sports complex whether the Kings are here or not," Mayor Kevin Johnson said Wednesday. "It's about our city and proving we can get big things done."

Sports financing experts caution that building an arena without a professional sports team would be difficult, but not impossible.

Not everyone wants to try. The new, fan-led fundraising drive does not concede the Kings' departure. The campaign began minutes after the Anaheim City Council voted Tuesday night to issue a $75 million bond package to pay for upgrades to that city's Honda Center and to help the Kings relocate to Southern California.

Local Jiffy Lube shops paid for six digital billboards to publicize the "Here We Build" effort to raise money for an arena, and the campaign was mentioned more than 300 times Wednesday on Twitter. More than $125,000 was raised in the effort's first few hours after it was launched by local sports radio host Carmichael Dave.

Although that's a sliver of the $300 million or so needed for a new arena, organizers said they're encouraged.

"We've been watching everybody drag their feet, thinking the Kings don't have anywhere to go, and now we know they do," said Tony Peric, an Internet manager and Kings fan who helped set up the group's website at meetup.com/herewebuild. "The Maloofs, they're not seeing what they need to see. They need to see money, they need to see commitment."

Some city leaders don't see the Kings as so crucial, however.

For weeks, Mayor Johnson and city business interests have said a push for a new arena – preferably downtown – should continue with or without the Kings. Some have even suggested it would be easier to sell the idea to the public without the Kings' owners in the picture.

The mayor has said he's willing to accept a Kings move, as long as the team pays the $77 million it owes the city. To that end, City Hall sent a letter to the Kings and the NBA on Wednesday asking for written confirmation that the loan would be repaid.

The Maloofs, who own the team, have told media outlets and the mayor they intend to pay off the loan if they leave. If they don't repay, the city takes ownership of Power sBalance Pavilion and a $25 million stake in the team.

"Perhaps if the Kings leave Sacramento, some of the frustration over the team and their future will go away and allow for a more reasonable discussion on the importance of a multi-use facility," said Michael Ault, executive director of the Downtown Sacramento Partnership.

Yet arena finance experts said the task of constructing a new facility without a professional sports team would be daunting. Luxury suites make up a big part of a facility's financial picture – and those who lease them want more than concerts and circuses.

"If the team goes away, so does the motivation for building a new building," said Gary Bongiovanni, the editor and chief of Pollstar magazine, which reports on the concert and arena industry.

Developer David Taylor, who is leading the city-backed analysis of a new arena, has acknowledged that putting up a new building would be tough without the Kings.

Still, Assistant City Manager John Dangberg told the City Council on Tuesday that Taylor and arena builder ICON Venue Group were "moving forward regardless of what happens in Anaheim."

Taylor and ICON have met with Inland American Real Estate Trust, owner of the 240-acre downtown railyard. As part of its analysis, the arena team has determined an arena could fit on a 24-acre parcel in the railyard owned by the city.

Arena backers point to Kansas City's 4-year-old Sprint Center as proof that an arena can succeed financially – even if it doesn't have a professional sports tenant. The facility is ranked by Pollstar as one of the busiest entertainment venues in the country.

To raise the $220 million needed for the arena, Kansas City imposed a $4-a-head fee on rental cars and hotel rooms. AEG, a concert promoter that is managing the arena, kicked in $54 million.

Shani Tate, the Sprint Center's director of marketing and ticket sales, said it has exceeded expectations for revenue and event bookings. Under a complicated revenue-sharing formula, the city received $4.1 million in "unanticipated profits" during the first three fiscal years of operation, in addition to user fees and taxes, she said.

"If you can find enough programming, (an arena without a team is) viable," said University of Oregon sports business expert Paul Swangard.

But it does make it harder.

"It's nice to have (a sports tenant) that can guarantee those 40 nights a year," Swangard said. "If you can't, you've got to find every rodeo, every monster truck, all those ancillary things."

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Call The Bee's Ryan Lillis, (916) 321-1085. Read his City Beat blog at sacbee.com/citybeat.