Democratic presidential candidate John Kerry has all but secured his party's nomination, with wins in nine out of 10 states that held contests Tuesday. One of his victories came in California, the most populous U.S. state and the biggest prize in the U.S. presidential election. President Bush and Senator Kerry will search for strategies to attract the vote in such key regions, while appealing to a national audience.

With the news that North Carolina Senator John Edwards planned to quit the race Wednesday, Senator Kerry savored his victory Tuesday evening. "Tonight the message could not be clearer all across our country: Change is coming to America," he said.

One change that Mr. Kerry wants is a Democrat in the White House. It's a change that President Bush hopes to prevent. Mr. Bush's supporters unveiled a television ad this week promoting the president's record. It says: "President Bush: Steady leadership in times of change."

Both men must maneuver an obstacle course between now and the election in November. As they travel the country campaigning, they must tailor their message regionally, addressing job loss in Ohio, which has seen much of its manufacturing move to developing countries. But candidates must promote trade in coastal states like California. What appeals to voters in one place may offend the voters in others.

Republican strategist Dan Schnur recalls Howard Dean's emotional speech to supporters in Iowa, and how it was viewed outside Iowa. Some who watched on television thought his excitement was excessive.

"As Howard Dean will tell you after his experience the night of the Iowa caucuses, you can't focus solely on the audience in the room because oftentimes there is a national or even international audience that is listening just as carefully," said Mr. Schnur.

A candidate may be criticized for style, and even more so for the substance of his or her positions.

Mr. Schnur believes same-sex marriage could become a disastrous issue for Democrats. Last month, San Francisco officials began to issue marriage licenses to gay and lesbian couples. Democrats tend to be more liberal on the issue than Republicans, and Democratic politicians try not to offend their liberal base while reaching out to voters in the political center.

President Bush has endorsed a proposal to amend the U.S. constitution, restricting marriage to a man and woman. That pleases some conservatives, but upsets others who think he is overreacting to the issue. Senator Kerry has already accused Mr. Bush of using the Constitution to divide the country.

Analyst Sherry Bebitch Jeffe sees a wild card in the election: the independent voters who are a growing minority in states like California. Democrats have an edge in the state, with 43 percent of registered voters to 36 percent of voters who are Republican. But the 16 percent who belong to no political party can potentially sway an election one way or another.

Ms. Jeffe says California independents are hard to classify. They are fiscally conservative, but liberal on social issues.

"So candidates cannot be big spenders, big taxers, but voters will allow taxation for programs that they care about, that they can oversee," she said. "So I think most candidates cannot be of the extremes to appeal to the middle of the voting electorate."

These analysts say diverse groups of voters respond to different issues, and that candidates run the risk of offending some as they appeal to others. They add that political rivals are always ready to highlight any misstep.