The pertinent issue here is that American citizens are presumed non-citizens unless they can prove otherwise. Proving citizenship requires the cooperation of a recalcitrant bureaucracy, often one held in the hands of Republican officials who have a partisan interest in disenfranchising Democratic voters. By changing the state Constitution, non-citizenship for voting purposes (although not for other things, such as tax obligations) becomes an entrenched principle that can't be thrown out by a judge.

http://www.nytimes.com/2008/05/12/us/politics/12vote.html?_r=1&pagewanted=all

The battle over voting rights will expand this week as lawmakers in Missouri are expected to support a proposed constitutional amendment to enable election officials to require proof of citizenship from anyone registering to vote

The measure would allow far more rigorous demands than the voter ID requirement recently upheld by the Supreme Court, in which voters had to prove their identity with a government-issued card.

Sponsors of the amendment -- which requires the approval of voters to go into effect, possibly in an August referendum -- say it is part of an effort to prevent illegal immigrants from affecting the political process. Critics say the measure could lead to the disenfranchisement of tens of thousands of legal residents who would find it difficult to prove their citizenship.

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. That number was included in election data obtained through a lawsuit filed by voting rights advocates and provided to The New York Times. 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.

"Three forces are converging on the issue: security, immigration and election verification," said Dr. Robert A. Pastor, co-director of the Center for Democracy and Election Management at American University in Washington. This convergence, he said, partly explains why such measures are likely to become more popular and why they will make election administration, which is already a highly partisan issue, even more heated and litigious.

The Missouri secretary of state, Robin Carnahan, a Democrat who opposes the measure, estimated that it could disenfranchise up to 240,000 registered voters who would be unable to prove their citizenship.

In most of the states that require identification, voters can use utility bills, paychecks, driver's licenses or student or military ID cards to prove their identity. In the Democratic primary election last week in Indiana, several nuns were denied ballots because they lacked the required photo IDs.

In it's first incarnation, the issue revolved around accusations of voter fraud. The only evidence of this purported voter fraud was size of registration lists for inner city neighborhoods. This phenomenon is common in precincts with low average times of residency, since voters move but their names stay on the rolls for their previous address.

A court case had originally been brought by the government, in which the Federal government was attempting to force the state to purge many of the names on its voter rolls, was dismissed. No evidence of voter fraud was ever presented by the government is this case, even though voter fraud was the proffered reason for the need to purge lists.

Although it's typical to assume that it's easy to obtain the documentation required in order to vote, there are some people who lack these documents. This small and often invisible subset of voters comprise a large enough percentage of voters to swing a close election.

Lillie Lewis, a voter who lives in St. Louis and spoke at a news conference last week organized to oppose the amendment, said she already had a difficult time trying to get a photo ID from the state, which asked her for a birth certificate. Ms. Lewis, who was born in Mississippi and said she was 78 years old, said officials of that state sent her a letter stating that they had no record of her birth.

"That's downright wrong," Ms. Lewis said. "I have voted in almost all of the presidential races going back I can't remember how long, but if they tell me I need a passport or birth certificate that'll be the end of that."