Navarro is not alone. Mexican immigrants eligible to become U.S. citizens are far less likely to naturalize than other major immigrant groups, limiting their political clout at a time when the Mexican immigrant population is booming in Arizona and the rest of the country, experts say.

But that is changing, in part because a wave of recent state and federal laws and proposals aimed at restricting benefits to immigrants is prompting more Mexican immigrants to become naturalized U.S. citizens, experts say.

In 1995, just 19 percent of eligible Mexicans had become naturalized U.S. citizens. In 2001, the most recent year for which data are available, 34 percent had done so, according to the Urban Institute, a nonpartisan research institute in Washington, D.C.

But they still lag other major immigrant groups.

Naturalization rates for immigrants from Europe and Canada held steady at about 65 percent. Asians had the highest naturalization rates: 67 percent in 2001 compared with 56 percent 10 years earlier.

In July 2003, Rep. Ed Pastor, D-Ariz., and other Hispanic members of Congress, launched workshops to help more immigrants apply for citizenship.

Since then, Pastor has held four workshops, most recently on Feb. 12, and completed 427 citizenship applications.

"My experience over the years is that if you make it convenient, people will come," Pastor said.

Navarro, a waitress at El Matador restaurant in downtown Phoenix, credited Pastor with prodding her to take the step. Every time Pastor ate at the restaurant, he would chide her, "When are you going to become a citizen?"

Navarro said she had the desire for years. But some big expense always got in the way. In 1993, her husband had heart surgery. In 1996, her mother needed an operation. In 1997, her father died.

Navarro finally filled out the paperwork last March. She paid the $390 application fee with her tax refund.

Randy Capps, an immigration expert at the Urban Institute, said low naturalization rates hurt Mexican immigrants politically because one of the biggest benefits of becoming a citizen is the right to vote.

"What that does is dilute Mexican voting power and generally disenfranchises the community," he said.

According to a 2001 Urban Institute study, Mexicans represented 28 percent of the nearly 8 million immigrants in the United States eligible to become naturalized citizens. But they represented only 9 percent of recently naturalized citizens. At least 190,000 of the immigrants eligible to become citizens live in Arizona, where the Mexican immigrant population now exceeds half a million people.

In contrast, Asians represented 27 percent of the immigrants eligible to become U.S. citizens but 43 percent of recently naturalized citizens, according to the Urban Institute.

There are many reasons why Mexican immigrants are slow to become U.S. citizens, said Michele Waslin, director of immigration policy research at the National Council of La Raza, a Latino advocacy organization in Washington, D.C.

The primary reason, she said, is because "a lot (of Mexican immigrants) come here thinking they will come here temporarily and return."

Economics also is a factor. In February 2002, the federal government increased the price of applying for citizenship to $390 from $310.

"It costs a lot of money to naturalize," Waslin said.

She said one of the reasons naturalization rates among Mexican immigrants are rising is out of fear. In the late 1990s, Congress passed laws that restricted legal immigrants' access to public benefits and made it easier to deport them, she said. And since the Sept. 11, 2001, terrorist attacks, the government has begun aggressively deporting immigrants who commit crimes.

"I think there is a fear factor involved there," Waslin said.

She said expanding civics and English classes could help improve naturalization rates. So could reducing federal backlogs.

In Phoenix, immigrants wait eight to 10 months for their citizenship application to be processed, said Al Gallmann, assistant district director of U.S. Citizenship and Immigration Services in Phoenix. As of the end of February, 5,600 citizenship applications were pending.

Despite the backlogs, the Phoenix office has seen a slight increase in citizenship applications. Since October, the start of the fiscal year, the office had received, on average, 469 citizenship applications per month, up from 442 per month the year before, Gallmann said.

As for Navarro, she celebrated her new citizenship with a sip of tequila. But first she registered to vote.