WEST PALM BEACH, Fla. — Mitt Romney and Senator McCain accused each other today of harboring liberal tendencies, a charge bordering on blasphemy in the increasingly caustic campaign for the Republican presidential nomination.

Mr. Romney struck first on the day before the winner-take-all Florida primary, criticizing the Arizona senator for his legislation reducing the role of money in politics, for his position on immigration, and for his support of an energy bill that he said would have driven up consumer costs.

“If you ask people, ‘Look at the three things Senator McCain has done as a senator,’ if you want that kind of a liberal Democratic course as president, then you can vote for him,” Mr. Romney told campaign workers. “But those three pieces of legislation, those aren’t conservative, those aren’t Republican, those are not the kind of leadership that we need as we go forward.”

Mr. McCain answered swiftly, accusing the former Massachusetts governor of “wholesale deception of voters. On every one of the issues he has attacked us on, Mitt Romney was for it before he was against it.”

He added, “The truth is, Mitt Romney was a liberal governor of Massachusetts who raised taxes, imposed with Ted Kennedy a big government mandate health care plan that is now a quarter of a billion dollars in the red, and managed his state’s economy incompetently, leaving Massachusetts with less job growth than 46 other states.”

Mr. McCain later told a Jacksonville audience that Mr. Romney has been “entirely consistent. He’s consistently taken at least two sides of every issue, sometimes more than two.”

The exchange reflected the stakes in tomorrow’s contest, a prelude to a virtual nationwide primary on February 5.

The polls show Messrs. McCain and Romney in a state race that is too close to call.

Mr. McCain collected endorsements in recent days from Florida’s top two Republican elected officials, Senator Martinez and Governor Crist, as well as the endorsements of a slew of Florida newspapers. The former Vietnam prisoner of war also has universal name recognition, as well as ownership of an issue important to the large number of veterans and active military in the state, national security.

But Mr. Romney has a get-out-the-vote effort in the state that has been at work on early voters as well as those seeking to cast absentee ballots.

A former businessman, he has campaigned as the man with the credentials to shore up the economy, a counter to Mr. McCain’s national security credentials.

Mayor Giuliani and a former Arkansas governor, Michael Huckabee, are also on the ballot, but recent surveys have shown them fading. Mr. Giuliani declined to join the fray.

“My opponents are fighting each other, calling each other names. Let them do that. We’re not going to call anybody names. I want Florida to send a message that the kind of candidate you want and the kind of president you want is one that can remain focused on positive goals,” Mr. Giuliani told an audience in Sanford, Fla.

Mr. McCain is expected to do well in areas with a strong military presence — Pensacola, Jacksonville, and Tampa. He’s also hoping for a strong turnout in Miami, with its Cuban-American population, and Orlando, a melting pot with a strong Puerto Rican community.

Mr. Romney is fighting for the southwest part of the state around Fort Myers and Sarasota; it’s much like the Midwest, where he was raised. Another likely stronghold for him, Palm Beach and Broward County, home to many Northeastern transplants.

Up for grabs is the corridor between Tampa and Daytona Beach along Interstate 4, a swing part of the state that has seen much growth and is home to roughly two-thirds of the Republican primary vote.

Mr. Romney was in West Palm Beach while Mr. McCain was in Jacksonville as they set out on their final full day of Florida campaigning.

Addressing phone bank workers who came out to the airport to see him off on a state flyaround, Mr. Romney said three key bills that Mr. McCain pushed in Congress steered the country on “a liberal Democrat course.”

Mr. Romney said the 2002 McCain-Feingold campaign finance law “hit the First Amendment” with its controls over advertising spending.

He labeled last year’s failed McCain-Kennedy immigration bill “the amnesty bill” because it would have allowed illegal immigrants to remain in the country indefinitely. Mr. Romney also said a 2003 McCain-Lieberman energy cap-and-trade bill would have increased energy costs for the average Florida family of four by $1,000.

He also drew chuckles from his audience when he recalled there was talk during the 2004 campaign of Mr. McCain teaming up with Senator Kerry of Massachusetts, the Democratic presidential nominee, on the opposing party’s ticket.

“Had someone asked me that question, there would not have been a nanosecond of thought about it; it would have been an immediate laugh,” Mr. Romney said. “And, of course, if someone asked him if he would consider me as a running mate, he would have also laughed immediately.”

During a news conference, Mr. Romney also criticized Senator Obama, who has drawn large crowds in his bid for the presidency.

Asked how he would counter Mr. Obama if he were the nominee, Mr. Romney said, “the nation will divide in two parts — politically at least.”

He said of his supporters: “Some may be less demonstrative in how they show their support for that vision, but I believe fundamentally that America is not interested in following a socialistic-style, government-run nation.”

Emphasizing his signature issue, Mr. McCain toured the grounds of Atlantic Machine, which builds Navy ships and commercial vessels, before holding a round-table in one of the company’s warehouses with national security experts, including a former CIA director, Jim Woolsey, and a former Veterans Affairs secretary, Tony Principi.

In his statement issued before the event, Mr. McCain likened Mr. Romney to Mr. Kerry over the weekend in a Web ad that superimposed the face of the former governor on an image of the 2004 Democratic presidential candidate windsurfing. The campaign also acknowledged that it has been running a radio ad statewide in Florida since Friday that assails Mr. Romney’s record.