A new proposal from a leading candidate for the Republican presidential nomination, Michael Huckabee, could make it a crime for hundreds of thousands of Americans to vote in foreign elections, perform military service in other countries, or even use a foreign passport.

The former Arkansas governor’s “Secure America Plan” includes a call to “discourage dual citizenship” by imposing “civil and/or criminal penalties on American citizens who illegitimately use their dual status.” While Mr. Huckabee’s plan is short on details, it says prohibited uses of dual citizenship would include “using a foreign passport, voting in elections in both a foreign country and the U.S,” and other actions.

Proponents of restrictions on dual citizenship have focused on the possibility that millions of Mexican Americans could soon have voting rights in both countries. However, one critic of Mr. Huckabee’s plan said the former governor may be unwittingly picking a fight with a wide array of migrants and descendants of migrants.

“The political problem with any proposal intended to police dual citizenship is you start getting into constituencies beyond the Mexican-American constituency,” a law professor at Temple University, Peter Spiro, said. In recent years, Americans with ties to Israel, Taiwan, Poland, Iraq, and other nations have voted in those countries in significant numbers. Some groups have even organized airline flights to allow expatriates to cast ballots.

Mr. Spiro said talk of a dual citizenship crackdown was likely to be a loser for Mr. Huckabee, at least in the long term. “Huckabee might get a little bit out of it in the context of Iowa, but not when you start moving to any state that has these other groups,” the professor said. “It’s a nonstarter. … It doesn’t make sense for any mainstream candidate to harp on this.”

Spokeswomen for Mr. Huckabee’s campaign did not respond to telephone calls and e-mail messages yesterday seeking more information on the proposal. However, the campaign announced that the plan was based largely on the work of a think tank favoring stricter limits on immigration, the Center for Immigration Studies.

“I’m actually very happy we’re having a debate about this,” a political science professor who has worked with the think tank on the dual citizenship issue, Stanley Renshon of City University of New York, said. He said he views dual citizenship and voting abroad as “a hindrance” to integrating new Americans into American society.

“The reason I’m against it is because it orients people to their home countries rather than to this country,” Mr. Renshon said. He said he has found no evidence that allowing Americans to vote abroad promotes democracy overseas.

Mr. Renshon, author of the 2005 book “The 50% American,” said he supports immigration but is concerned that some immigrants and even some children of immigrants view the ties to their countries of origin as equal to or more important than their ties to America. “The trouble is a lot of people are taking a pan-ethnic, pan-racial identification and then taking it on into the second generation,” the professor said.

Reaction to the dual-citizenship proposal from immigrant groups, who are often fearful of allegations of dual loyalty, has been muted thus far. “We actually are not supportive of dual voting,” a spokeswoman for the National Council of La Raza, Lisa Navarette, said.

In 2005, a Republican member of Congress of Arizona, John Hayworth Jr., introduced a bill that included language that would have imposed up to a year in prison or a fine of up to $10,000 on naturalized American dual nationals for voting in foreign elections, running for elective office or serving in any governmental capacity abroad, using a foreign passport, or serving in the armed forces of their second country.

The bill racked up 33 co-sponsors in the House but never made it out of committee.

Critics of dual nationality have generally focused on naturalized Americans because they are required to take an oath under which they “absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty.”

The penalties in the 2005 bill were aimed at those who took the oath, but the ex-governor’s vague proposal left open the possibility that it might apply to people who acquire two or more nationalities at birth.

If Mr. Huckabee’s plan would bar military service abroad, it could anger some American Jews who serve in the Israel Defense Force. Mr. Renshon said he has fielded such complaints from Jewish Americans. “I’m Jewish myself. I still feel everyone in this country really should be required to focus their energy and attention here,” he said.

Another Republican presidential candidate, Thomas Tancredo, has also denounced the concept of dual citizenship. “It’s horrible idea,” he said in a 2003 interview with a Web site, Right Wing News. Mr. Tancredo co-sponsored the 2005 bill and, according to the Ames Tribune, campaigned on the issue while in Iowa in July.