For Rudy Giuliani, Jan. 29 may be the most important date since Sept. 11.

That's when Florida Republicans vote in the primary on which the former New York mayor has staked the entire future of his struggling presidential campaign.

It's the crucial test for a strategy most analysts have derided. Only the muddled nature of the GOP race gives Giuliani any hope of pulling it off. Florida will determine if the man who built his candidacy on his handling of the 2001 terrorist attacks remains a serious contender. Otherwise, the GOP race may quickly come down to an insider-outsider contest between Sen. John McCain and former Gov. Mitt Romney.

In essence, Giuliani decided to challenge historical precedent by bypassing Iowa, New Hampshire and South Carolina. He calculated that a former big-city mayor who failed to share his party's opposition to abortion rights and gun control was unlikely to do well there, despite a split among his conservative rivals.

Efforts to flout tradition — the Iowa-New Hampshire role in defining the race — failed for past candidates, from Phil Gramm to McCain.

But Giuliani reached his decision only after spending a lot of time and money in all three states, especially New Hampshire.

He gambled that his early lead in national polls — and his strength among party moderates in such key Feb. 5 states as New York, New Jersey and California — would hold up while his rivals knocked one another out in those early tests.

That's not what happened. The highly publicized results in the early states created a new national pecking order that superseded the early numbers built primarily on name identification and Giuliani's post-Sept. 11 fame.

That catapulted McCain, the New Hampshire and South Carolina winner, and Mike Huckabee, the Iowa winner, to the top of the GOP field. Giuliani suffered the embarrassment of pulling fewer votes in some states than GOP maverick Ron Paul.

In addition, the former mayor's support has begun to drop in his supposed coastal strongholds. Recent polls show him far behind in California and Connecticut and roughly even in New Jersey.

Even more ominously, two polls this week in New York, his home state, showed him a dozen points behind McCain (two others showed it roughly even) in the wake of the senator's victory Saturday in South Carolina.

On Tuesday, McCain unveiled strong support in all three New York-area states, including from former New York Sen. Al D'Amato, no friend of Giuliani.

The Florida result undoubtedly will affect what happens Feb. 5. And Giuliani may yet benefit from the two weeks he invested there while his rivals were battling in Michigan, won by Romney, and South Carolina.

Polls show McCain narrowly ahead in a tight four-way race, with a spread from top to bottom of less than 10 points. But campaigning this week could change that.

One thing that could help Giuliani is a renewed emphasis on economic issues. He is pushing the kind of big tax cut that always has appealed to Republican voters and has attacked McCain for voting against the Bush tax cuts and backing Democratic alternatives.

Giuliani hopes, as does Romney, that McCain will be hurt in Florida by the fact that independents can't vote in the GOP primary as they did when they helped him win New Hampshire and South Carolina.

Some past candidates have done poorly in the early primaries but emerged later as top contenders. That was true for Ronald Reagan in his near-miss 1976 bid and for Bill Clinton against a fairly weak Democratic field in 1992.

Indeed, the flaws of the other GOP candidates give Giuliani hope in Florida. McCain has encountered resistance from social conservatives. Romney has won only states where he had an inherent advantage, such as his boyhood home state of Michigan, or where his rivals largely abstained.

Huckabee, short on funds, has been unable to rekindle the enthusiasm among social conservatives that he did in taking Iowa.

So despite Giuliani's early failures, former Maryland Gov. Bob Ehrlich was probably right when he said on MSNBC that if the mayor wins in Florida, "it's a whole new ball game."

Beyond that, it certainly would be another blow to those of us who said the Giuliani strategy was hopelessly flawed — and to the power Iowa and New Hampshire have exercised for a generation.

Carl P. Leubsdorf is Washington bureau chief of the Dallas Morning News. Reach him at cleubsdorf@dallasnews.com.