As it drives to regain political power, the Republican Party depends on what goes on behind the closed doors of an austere 12th-floor office suite in downtown Washington.

The office is marked only by a sign reading "American Crossroads" and "American Action Network." But behind the nondescript entrance is the headquarters of a new political power: a fundraising operation that has pulled in more than $32 million this year, as well as sophisticated marketing, research and advertising operations - all aimed at getting Republicans elected to the House and Senate.

The organizations have been created outside the official party apparatus. They duplicate almost all the functions of the traditional GOP while often taking advantage of legal provisions that allow them to conceal the names of those who foot the bill.

American Crossroads and its affiliates are the offspring of George W. Bush administration strategist Karl Rove and other senior GOP leaders who once worked within the regular party structure, especially the Republican National Committee and its tradition-encrusted headquarters near the Capitol.

Other independent groups - such as Americans for Prosperity and FreedomWorks - have sprung up with operations often tailored closely to the wishes of their conservative supporters, some of them billionaire businessmen. Crossroads officials say they work with more than 20 other conservative organizations, including the U.S. Chamber of Commerce and Americans for Tax Reform, to make sure money is spent effectively.

Many of the new groups were formed after the Supreme Court's Citizens United decision last year, which made it easier for corporations and unions to spend directly on political causes. New groups formed on the left and right, but the dramatic growth has been on the right.

Some, including American Crossroads, organized initially under a provision of the tax code that required them to disclose their donors. Later, however, Crossroads added a nonprofit affiliate, Crossroads GPS, that does not have to disclose its donors. Crossroads GPS, the U.S. Chamber of Commerce and Americans for Prosperity do not disclose the names of donors, and they are growing rapidly.

On the Democratic side, labor, environmental and other allied groups have long worked on behalf of the party's candidates. But the Democratic-leaning groups have usually functioned as informal partners with the party organization, while this year's conservative organizations have largely rejected the leadership of the Republican National Committee and its Capitol Hill operations.

For many veterans of GOP politics, the Republican National Committee under its controversial chairman, Michael Steele, has been ineffective in fundraising and providing manpower in battleground races.

The new organizations appear to have stolen a march on the Democrats. Organized labor and other Democratic-leaning groups are only now running commercials with significant campaign-related messages. As of last week, more than twice as much had been spent on television ads favoring Republican candidates as had been spent on ads for Democrats ($36 million to $16 million), according to the Campaign Media Analysis Group.

American Crossroads and Crossroads GPS have already run millions of dollars in advertising in nine Senate races in California, Illinois, New Hampshire and other states. Washington state and Florida ad blitzes are likely to be announced soon.

Crossroads expects to move heavily into more than two dozen House races, including those in Ohio, Pennsylvania, Florida and possibly California.

Some of the $31.6 million raised by Rove and his allies for the Crossroads groups also is going into a grass-roots campaign network that promises unprecedented coordination with business and conservative groups, strategies to monitor new early voting rules and a new database that will allow precise targeting of likely conservative voters. It would then generate 20 million phone calls and 40 million pieces of mail to get them to vote.

Steven Law, a Bush administration and campaign veteran, runs the Crossroads groups. Former RNC Chairman Mike Duncan serves as Crossroads board chairman. In the same suite, Norm Coleman, the former Minnesota senator, runs American Action Network, which hopes to raise $25 million this year.

So far, the conservative groups have raised and spent more money than labor and the Democrats, even though the latter went into the campaign season with a clear financial advantage.

Democrats acknowledge that the independent conservative groups are making a difference. A memo circulating among House Democrats shows that as of Sept. 14, outside Republican groups had reserved air time for $22.4 million in advertising in key House races, compared with Democrat-aligned groups reserving just $3 million through mid-October for the same contests.

In Colorado, American Crossroads, the Club for Growth and the U.S. Chamber of Commerce sponsored ads last week for Ken Buck, the Republican Senate candidate. Only one group, the Democratic Senatorial Campaign Committee, was on the air for Democratic Sen. Michael Bennet.

In Nevada, American Crossroads took credit for buoying Republican Senate candidate Sharron Angle, with approximately $2 million in ads in her race against well-funded Senate Majority Leader Harry Reid. "Our ads helped keep the race competitive after the primary when Reid was going for an early knockout," Law said.

In California, where Sen. Barbara Boxer has enjoyed a fundraising advantage over Republican challenger Carly Fiorina, outside groups have helped Fiorina close the gap.

Boxer's campaign manager, Rose Kapolczynski, said the outside groups essentially provided "$3 million in free advertising for the Fiorina campaign" at a time when Fiorina didn't have the resources to go on the air herself.

The antiabortion Susan B. Anthony Fund plans to double the $3 million it spent nationally in 2008, including $1 million to defeat Boxer. Already Crossroads GPS has aired $1 million worth of advertising. The U.S. Chamber of Commerce plans to spend several million dollars against Boxer, and other conservative groups have made pledges as well.

"This is why this may last longer and be more competitive than Barbara Boxer's previous races," said political science professor Bruce Cain of UC Berkeley. "In the past, you could close out the opposition by building up a lead early on and then donors would stop giving."

Kapolczynski said the influx of outside money has had an upside in helping galvanize Boxer's supporters, particularly after ads aired sponsored by Crossroads GPS, with its known ties to Rove. "Karl Rove coming into California to campaign against Boxer was a wakeup call to a lot of our supporters," she said.

Jim Jordan, a former director of the Democratic Senatorial Campaign Committee, said spending by the Republican-allied groups this year had led him and a group of other Democrats to form their own organization, Commonsense Ten.

"Being outgunned six or seven or eight to one in independent expenditures really is a recipe for disaster, especially in this political climate," Jordan said.

His group, which discloses its donors, is up with its first ads - in Missouri and Washington state. But it is a small start against Crossroads and Crossroads GPS, which plan to raise more than $50 million.

Times staff writer Maeve Reston in Los Angeles contributed to this report.

tom.hamburger@latimes.com

richard.simon@latimes.com