LOS ANGELES — Republican presidential candidate Mitt Romney readied plans to run a "significant" level of television ads in California and other states that vote Tuesday in essentially a national primary, signaling an intention to aggressively try to derail Republican front-runner John McCain.

Unwilling to cede his lead, aides to the Arizona senator said he, too, was preparing to run a high volume of commercials on national cable channels and in key states.

The upcoming TV advertising campaigns for both candidates underscore the fierce battle for the GOP nomination ahead of the 21 states that hold GOP primaries and caucuses next week. Running ads coast to coast is a multimillion-dollar venture; thus both campaigns were precisely targeting their commercials to states they think they can win and that offer them the most delegates. The candidates were spending Thursday working out their final strategies.

Since his defeat in Florida Tuesday, Romney has been debating how much of an effort to make against McCain. The former Massachusetts governor is trying to get back on track after two straight losses to McCain — in South Carolina on Jan. 19 and more recently in the winner-take-all state of Florida. That victory gave McCain the advantage in the all-important delegate count as well as the momentum in the GOP race.

After seven contests, Romney is down narrowly — 83-59 — with 1,191 national convention delegates needed to secure the nomination and 1,023 up for grabs Tuesday. So, Romney has decided to try to cobble together wins in enough states Tuesday to topple McCain in the delegate count, or at least remain relevant.

California has 170 delegates at stake Tuesday; candidates are awarded three for each congressional district they win. The state is incredibly expensive to compete in but Romney aides argue that he can win some districts here.

In a debate Wednesday night in Simi Valley, Calif., Romney tried to cast himself as more conservative than McCain and argued that his rival's record too frequently deviated from the party line — a preview, perhaps, of the advertising message in the coming days.

"There are a number of pieces of legislation where his views are out of the mainstream, at least in my view, of conservative Republican thought," Romney said.

McCain shot back: "I'm proud of my conservative record."

For now at least, Romney will run an ad in California starting Friday in which he portrays himself as the Republican most able to take on Democratic candidate Hillary Rodham Clinton.

"She hasn't run a corner store, she hasn't run a state, she hasn't run a city," Romney says in the ad. "I have spent my life running things. I've learned how to run a business, I've learned how to run a state, I ran the Olympics, in each case I've brought change."

Romney's advisers had given him several options, ranging from $1 million in ads to $7 million in ads for an expensive multistate effort. It was not immediately clear how much money Romney was willing to spend — or whether the multimillionaire would dip into his own bank account again.

His wealth is estimated at up to $250 million, and he has poured some $35 million into his presidential campaign. The former venture capitalist has stated publicly that he and his wife have agreed on a personal spending cap, though they refuse to divulge the figure.

Romney's travel schedule reflects his campaign targets — if not his advertising goals.

With his opportunity for scoring the nomination dwindling, Romney's strategy calls for seeking votes in states with heavy concentrations of Romney's fellow Mormons: California, Arizona, and Utah, seat of The Church of Jesus Christ of Latter-day Saints.

Romney, trying to become the first Mormon elected president, will attend the funeral of the church President Gordon B. Hinckley on Saturday in Utah.

He will also campaign Friday in Colorado, followed by visits to Minnesota, Illinois and Missouri, key midwestern battlegrounds. In Missouri, a classic swing state, Romney enjoys the strong support of Gov. Matt Blunt.

Also on the tentative schedule were Tennessee and Georgia, Southern states where Romney has shown strength. Romney was likely to bypass delegate-rich New York and New Jersey after former New York mayor Rudy Giuliani decided to drop out of the race and support McCain.

Romney's home state of Massachusetts also votes Tuesday. His campaign tentatively planned to receive the Super Tuesday returns there. If he were to fail, Boston would be the most likely sight of his campaign goodbye.

Along with targeted ads, McCain is planning to rely on momentum and "free" news coverage that comes with it by holding rallies and news conferences in California and big winner-take-all delegates states, including New York and Illinois. McCain picked up the endorsement of California Gov. Arnold Schwarzenegger on Thursday, an event sure to garner loads of publicity.

With winner-take-all states his first priority, McCain's tentative travel schedule calls for him to travel coast to coast for general-election style rallies in Missouri, Illinois, Tennessee, Alabama, Georgia, Massachusetts, New Jersey and New York.

Associated Press Writer Glen Johnson contributed to this report.