The number of legal immigrants seeking to become United States citizens is surging, officials say, prompted by imminent increases in fees to process naturalization applications, citizenship drives across the country and new feelings of insecurity among immigrants.

The citizenship campaigns have tapped into the uneasiness that legal immigrants, especially Hispanics, say is a result of months of debate over an immigration bill that failed last week in the Senate. Although illegal immigrants were the center of attention in the debate, it prompted many legal immigrants who have put down roots here to seek the security of citizenship, as well as its voting power, immigrants’ advocates said.

The numbers of new naturalized citizens have steadily grown, to 702,589 last year from 463,204 in 2003. A big jump occurred this year, with the number of applications increasing every month, to 115,175 in May compared with 65,782 last December.

More than 4,000 new Americans were sworn in yesterday in tradition-steeped — and some not so traditional — Fourth of July ceremonies. About 1,000 people from 75 countries took their oaths together under the turrets of Cinderella’s Castle at Walt Disney World in Lake Buena Vista, Fla., as Gloria Estefan sang “The Star-Spangled Banner.”

In Iraq, 325 foreign-born soldiers who are fighting in the United States military took the oath of allegiance in two ceremonies.

For many legal immigrants, worry about their futures in the United States turned into action after an announcement on Jan. 31 by Citizenship and Immigration Services that it would increase application fees.

Under the new fees, which take effect on July 30, it will cost $675 to become a naturalized citizen, up 69 percent from $400.

Immigrants have also been mobilized to press naturalization applications by a television and radio campaign that Univision, the national Spanish-language network, began in January in California.

The campaign, promoted by personalities like Eduardo Sotelo, a radio host in Los Angeles known as El Piolín, or Tweety Bird, has directed immigrants to 350 workshop centers run by churches and other community organizations in 22 cities. At the centers, immigrants receive English lessons and advice on meeting requirements and filling out forms.

One radio listener was Ángel Iván Álvarez, 24, a legal immigrant from Mexico who said he had never thought of becoming a citizen until last week when the Senate bill failed.

The measure, a bipartisan compromise supported by President Bush, would have created a path to legal status for illegal immigrants, among other actions.

After it failed, Mr. Álvarez, a real estate agent from Whittier, Calif., took down information from El Piolín’s show and registered in a citizenship workshop.

“I realized that I want to be able to vote and speak up for my people, because they are not getting enough support,” Mr. Álvarez said yesterday in a telephone interview. “I want everybody to be able to come out of the shadows.”

Federico Gutiérrez, 53, a longtime legal resident of Chicago who was born in Mexico, said large protests in March 2006 in support of an immigration overhaul made him decide that it was time to engage in American politics.

When the debate turned angry, Mr. Gutiérrez said, he wanted to be able to influence lawmakers who he believed favored immigrants.

He prepared his application and brushed up on his English and American history in classes offered by the New Americans Initiative, a citizenship campaign financed by Illinois. He became a citizen in May.

“Now if I don’t like the way things are going, I can let the government know my opinion,” Mr. Gutiérrez said in a telephone interview.

Some legal immigrants, particularly Hispanics, have said they were unfairly tarred in the debate over the Senate bill, which failed in part because of vehement opposition from conservatives who said it offered blanket amnesty to illegal immigrants.

“A lot of people who are here legally are made to feel like lepers,” said Rachel Duverge, 24, a Florida resident born in the Dominican Republic who was among the new citizens sworn in yesterday at Walt Disney World.

Ms. Duverge said she became a citizen in part because she was eager to vote in the presidential election next year. President Bush, she said, “has not handled immigration well.”

To become citizens, immigrants have to be legal permanent residents who have lived continuously in the United States for five years. They cannot have a criminal record and must pass tests to show proficiency in English and a basic knowledge of American history and government.

Advocates for immigrants say the increase in fees has been a decisive incentive for working-class immigrants to take action, especially when more than one family member is eligible to be a citizen.

“Before they said, ‘I can do it anytime,’ ” said Catherine Salgado, a spokeswoman for the Illinois Coalition for Immigrant and Refugee Rights in Chicago. “Now it’s not anytime anymore.”

Ms. Salgado said the $675 fee was a week’s wages for many immigrants who had applied for naturalization through workshops organized by the coalition.

The immigration agency is also remaking its civics and English tests, and many immigrants say they fear that the tests will be more challenging.

The Univision campaign had greater effects than its organizers expected, especially in California, said Maryam Banikaram, chief marketing officer for the company. Ms. Banikaram said the effort was part of its regular nonpartisan public service efforts of the company.

“If you become a U.S. citizen, you have better opportunities,” she said. “We’re just giving you the tools to make that a reality.”

The campaign took off after the immigration debate became major news for Univision and Mr. Sotelo, or El Piolín, used his racy comic radio show as a soapbox to support legal status for illegal immigrants.

Other immigrants are concerned about locking in economic gains that they have made as legal residents.

“A prime motivator is security for the family and for employment,” said Javiér Angulo, director of civic education for the National Association of Latino Elected and Appointed Officials Educational Fund, which organized workshops in connection with the Univision campaign. “People don’t feel that being permanent residents is enough to secure their future in this country. They would just feel more secure as citizens.”

In Chicago, Mr. Gutiérrez said he started life in a corn-growing village in central Mexico and had worked in factories most of the time since entering the United States in 1979. He has two adult children who are United States citizens.

“I will always have Mexican blood,” Mr. Gutiérrez said, enjoying a day of rest on his first Fourth of July as an American citizen. “But my heart is here.”