From Voter ID to Proof of Citizenship:

The State of Missouri may adopt a state constitutional amendment requiring proof of citizenship for voting. As the New York Times reports, the stated purpose of this requirement is to prevent voting by illegal immigrants and other non-citizens.

Voting experts say the Missouri amendment represents the next logical step for those who have supported stronger voter ID requirements and the next battleground in how elections are conducted. Similar measures requiring proof of citizenship are being considered in at least 19 state legislatures. Bills in Florida, Kansas, Oklahoma and South Carolina have strong support. But only in Missouri does the requirement have a chance of taking effect before the presidential election.

In Arizona, the only state that requires proof of citizenship to register to vote, more than 38,000 voter registration applications have been thrown out since the state adopted its measure in 2004. . . . More than 70 percent of those registrations came from people who stated under oath that they were born in the United States, the data showed.

Already, 25 states, including Missouri, require some form of identification at the polls. Seven of those states require or can request photo ID. More states may soon decide to require photo ID now that the Supreme Court has upheld the practice. Democrats have already criticized these requirements as implicitly intended to keep lower-income voters from the polls, and are likely to fight even more fiercely now that the requirements are expanding to include immigration status. . . .

Measures requiring proof of citizenship raise the bar higher because they offer fewer options for documentation. In most cases, aspiring voters would have to produce an original birth certificate, naturalization papers or a passport. Arizona and Missouri, along with some other states, now show whether a driver is a citizen on the face of a driver's license, and within a few years all states will be required by the federal government to restrict licenses to legal residents.

Critics say that when this level of documentation is applied to voting, it becomes more difficult for the poor, disabled, elderly and minorities to participate in the political process. . . .

Supporters of the measures cite growing concerns that illegal immigrants will try to vote. They say proof of citizenship measures are an important way to improve the accuracy of registration rolls and the overall voter confidence in the process. . . .

From October 2002 to September 2005, the Justice Department indicted 40 voters for registration fraud or illegal voting, 21 of whom were noncitizens, according to department records.

Welcome to the next round of debate and litigation over voter identification.