Galvanized by the lightning-in-a-bottle success of conservative “tea party” candidates, moderate Republicans and others in the political center are looking for ways to push back against what they see as an advancing tide of ideological extremism.

The efforts are loosely organized and embryonic, but politicians, advocacy groups and others are piecing together a framework to promote moderate candidates and advance positions they say have been eclipsed by partisan sniping on the right and left.

“Middle America is being ignored by Washington and the media. Centrists are desperate for a voice today; they feel entirely unrepresented,” said Mark McKinnon, a political strategist and former advisor to President George W. Bush.

“The tea party has tapped into voter frustration and anger,” he said, “but does not represent millions of Americans in the vast middle.”

The moves reflect political divisions that have only grown deeper as tea-party-backed insurgents have toppled candidates supported by the GOP establishment around the country.

Michael R. Bloomberg, the billionaire mayor of New York and possible future presidential candidate, has labeled the tea party movement a “fad” and a “boomlet.” He has vowed to use his personal popularity, his reputation as a pragmatic voice, and his wealth to promote Democratic and Republican moderates as candidates this fall.

At the same time, once-solid Republicans left behind as their party tacked rightward have launched independent bids in several states — including Alaska, Florida, Rhode Island and Minnesota — appealing to moderate voters.

Underscoring those efforts is a newfound drive by advocacy groups to give moderate voters a louder voice. In Washington, a nonprofit group called No Labels is forming with the goal of bringing Republicans and Democrats together; echoing tea party rhetoric, it terms itself a “citizens movement” and decries “the tyranny of hyperpartisanship.”

Bloomberg began to campaign on behalf of others after tea party activist Christine O’Donnell beat moderate Republican Rep. Michael N. Castle, a Bloomberg favorite, in Delaware’s Republican Senate primary this month.

Bloomberg first traveled to Rhode Island, to promote former Republican Sen. Lincoln Chafee’s independent campaign for governor. He followed up with a fundraiser at his New York home for Senate Majority Leader Harry Reid (D-Nev.), who is running against tea party Republican Sharron Angle. Bloomberg also plans to fly to California soon to campaign for gubernatorial candidate Meg Whitman, a Republican.

Bloomberg, a Democrat-turned-Republican-turned-independent, has more plans to support moderates who fit his model. He’s expected to back Rep. Mark Steven Kirk (R-Ill.), chasing an open Senate seat in Illinois, as well as Sen. Michael Bennet (D-Colo.), who faces a challenge from tea-party-supported candidate Ken Buck.

Howard Wolfson, a Bloomberg advisor, said the mayor would support candidates who are “willing, able, and interested in reaching across the aisle and working in a bipartisan way, whether they are Democrats or Republicans or independents.”

“The two parties aren’t even talking to each other,” Wolfson said. “He believes it’s critical to restore some degree of bipartisanship.”

Bloomberg is especially supportive of candidates who share his interest in issues such as education, immigration reform and gun regulation. He also favors candidates with business backgrounds, such as Whitman, said Wolfson, a former strategist for Secretary of State Hillary Rodham Clinton’s presidential campaign.

In Rhode Island, Bloomberg’s visit was a boost for Chafee, once among the Senate’s vanishing breed of liberal-leaning Republicans. Bloomberg “provided some real credibility for us,” said Chafee’s spokesman, Michael Trainor.

“With the polarization of the two parties,” Trainor said, “independent candidates provide a safe harbor for a lot of voters who are troubled by the extreme direction either party has taken.”

Independent candidacies have struggled in modern politics, mainly because of financial disadvantages. Independents also are unable to benefit from a party’s infrastructure, including get-out-the-vote efforts.

Chafee, like Republican Sen. Lisa Murkowski in Alaska and Gov. Charlie Crist in Florida, enjoys the advantage of widespread name recognition. Murkowski, in fact, is relying almost entirely on that advantage. Defeated in the state’s Republican primary by tea-party-backed Joe Miller, she can only win if enough people vote for her as a write-in candidate.

In announcing her write-in campaign this month, Murkowski said voters wanted an alternative to Miller and Democrat Scott McAdams. “They told me that we cannot accept the extremist views of Joe Miller,” she said.

Crist left the Florida GOP after badly trailing tea-party-backed Marco Rubio in the race for the party’s Senate nomination.

In Minnesota, ex-Republican Tom Horner’s independent gubernatorial bid has been buoyed by a growing discomfort with tea-party-backed Republican Tom Emmer and Democratic nominee Mark Dayton.

“Emmer is too far to the right and Dayton is too far to the left,” said Peggy Burnet, who hosted more than 200 at a Horner fundraiser last week in her Wayzata, Minn., home.

A longtime Republican, she said the current GOP did “not represent the whole Republican Party anymore. I think there are many of us who feel that way.

“When you’re in the middle, there really isn’t something representing you,” she said.

The No Labels effort, expected to launch later this year, is backed by Republicans such as McKinnon, the former Bush advisor, and Nancy Jacobson, a powerful Democratic fundraiser married to pollster Mark Penn.

Another Washington group, think tank Third Way, advocates “a moderate ideology” built around such issues as free trade and clean energy.

“If we allow polarization to continue on the path it’s on, we won’t be able to solve the problems our country is confronting,” said Anne Kim, a policy analyst for the organization.

joliphant@latimes.com