The most influential political strategist of the 2012 campaign works out of an unmarked suite in an anonymous office park in suburban Virginia, a few floors above a Japanese-themed steakhouse. He does not work for one of the presidential campaigns. He is not a pundit.

But Carl Forti, a low-profile Buffalo native who served as the political director of Mitt Romney’s first White House campaign, will deploy at least $400 million in political money this season, more than Sen. John McCain spent running for president in 2008.

After years in the Republican Party trenches, Forti, 40, is now a consultant and strategist for the biggest of the outside groups and “super PACs” that are rapidly displacing parties as the means for raising and spending vast amounts of political money.

In those roles, his work embodies the coordinated punch brought by like-minded groups to the effort to oust President Barack Obama and give Republicans full control of Congress.

And as a veteran of Romney’s inner circle, he brings to the effort a keen understanding of the Romney campaign’s needs even as he is barred by campaign finance law from working directly with it.

Forti is the political director of American Crossroads, the super PAC founded by his mentor, Karl Rove; Forti’s firm, the Black Rock Group, is a consultant to tax-exempt groups like the 60 Plus Association, which are expected to spend millions of dollars on ads this fall; and he is a founder of Restore Our Future, the super PAC that helped Romney in his bid for this year’s Republican presidential nomination.

Now, with Romney prohibited from spending much of the cash he is raising until after the Republican convention in August, Forti and his clients are filling in the breach: Crossroads Grassroots Policy Strategies, Restore Our Future and other Forti-linked groups have spent at least $35 million on advertising in 17 states against Obama since early April, according to the Campaign Media Analysis Group.

On Thursday, American Crossroads announced that it would begin a $9 million, nine-state campaign defending Romney against the Obama campaign’s attacks on his tenure at Bain Capital. The ads signify a pronounced shift in strategy for Crossroads, which has spent heavily on advertising attacking Obama, and demonstrate how super PACs and outside groups can synchronize with the candidates they support without violating federal rules that prohibit direct coordination.

“What happened to Barack Obama?” the narrator in the ad asks. “The press and even Democrats say his attacks on Mitt Romney’s business record are misleading, unfair, and untrue.”

Rove and others crisscross the country raising most of the money, tapping a network of wealthy conservatives and business executives determined to see Obama defeated. But at Crossroads and Restore Our Future, it is chiefly Forti who figures out how to spend it.

Drawing on his political acumen and knowledge of the swing-state political terrain built over three election cycles at the National Republican Campaign Committee, which oversees Republican strategy for House races, Forti trolls through reams of polling data, picks targets, approves scripts and helps negotiate with television stations for airtime in significant markets.

Most of the advertising has been placed through a company called Crossroads Media, founded by one of Forti’s Black Rock partners and housed in the same office suite. So far this cycle, Crossroads and Restore Our Future have broadcast ads in about 40 Senate and House races as well as the presidential race, officials at the groups said, a breadth unmatched in the world of independent spending.

“We came up through the party infrastructure, where you are forced to look at the entire national battlefield,” said Brian O. Walsh, a friend and former colleague of Forti’s who directs the American Action Network, a tax-exempt group closely allied with Crossroads.

American Crossroads and its tax-exempt affiliate, Crossroads GPS, are expected to spend $300 million on the presidential campaign and Senate races; Restore Our Future is planning to raise at least $100 million and possibly more. Americans for Job Security, a tax-exempt trade association that spent $9 million in 2010 but is not required to release the names of its donors, shares office space with Black Rock and retains one of Forti’s partners as a consultant.

Forti, whose clients prize his discretion almost as much as his expertise, declined to be interviewed for this article. But he is well known to watchdog groups tracking the explosive growth of outside spending this year — and is feared by the Democratic candidates who have been pummeled by Crossroads ads.

“He’s pretty good at keeping his name out of the papers,” said Melanie Sloan, the executive director of Citizens for Responsibility and Ethics in Washington. “He needs big donors to know he’s there — and no one else.”

Forti also helps lead a monthly meeting known as the Weaver Terrace Group, where officials from a variety of conservative groups, like the American Action Network, gather at the Crossroads offices to plan their political spending. (Several other groups that attend, like Americans for Tax Reform and the Republican Jewish Coalition, have also received large grants from Crossroads, enabling them to run their own large-issue ad campaigns.)

The meetings allow an extraordinary level of coordination on the right: Over the last month or so, conservative groups have taken turns pounding Obama in critical states like Florida, Iowa and Michigan, the advertising buys dovetailing to ensure a constant barrage. And the enormous budgets that Crossroads and its allies now command allow for high-quality advertising with production values on a par with presidential campaigns, said several consultants who work for outside groups.

Forti’s own career is a case study in the evolution of unrestricted money and outside groups from the margins to the mainstream of American politics. He spent seven and a half years at the House campaign committee. In his last year, 2006, he supervised its $80 million “independent expenditure” campaign, so called because the spending is financed by the party but cannot be coordinated with the party’s candidates.

Congressional scandals and the war in Iraq helped turn that election into a Democratic rout, with Republicans losing control of the House of Representatives. But the effort cemented Forti’s reputation as a master of the complicated legal and logistical demands of independent spending.

“He’s a Gatling gun,” said Thomas M. Reynolds, a former Republican congressman from New York who was chairman of the House committee that year. “He’s got multiple races going at any given time. Carl’s unflappable, disciplined, and focused.”

During the race for the 2008 Republican presidential nomination, Forti was Romney’s political director, serving alongside the two men with whom he founded Restore Our Future last year: Charles R. Spies, the campaign’s chief counsel, and Larry McCarthy, a veteran ad creator. When Romney dropped out of the 2008 race, Forti signed on with Freedom’s Watch, a conservative group that spent at least $30 million in an effort to counterbalance liberal groups like MoveOn.org.

Forti has often worked at the edge of the regulatory envelope that governs outside spending. Freedom’s Watch ignored a demand from the Federal Election Commission that it disclose its finances, after reports that the casino billionaire Sheldon Adelson had provided virtually all of the group’s financing and was directing its political spending, a circumstance that would normally have stripped the tax-exempt group of its right to keep its donors private. (The commission’s Republican and Democratic members deadlocked on pursuing the investigation, leaving the group’s finances undisclosed.)

In 2009, after Forti founded the Black Rock Group with two other Republican consultants, the company sought a legal opinion from the election commission that would have allowed it to solicit money from donors and coordinate spending without registering as a political committee. The proposal, which would have allowed the donors to spend money on political advertising without being subject to contribution limits, was not approved.

© 2012 The New York Times Company