The obscure rules of elections will be under intense scrutiny on Tuesday as civic groups, political parties and the Department of Justice, concerned about fair play, monitor polling places for irregularities.
New rules to limit same-day registration or require photo identification will be in effect in some states, even as their constitutionality is argued in the courts. Most of the changes were adopted by Republican legislatures in the name of electoral integrity, even though evidence of voter fraud was negligible. They are opposed by Democrats who say tighter rules are aimed at discouraging minorities, poor people and college students from voting. All those groups tend to prefer Democrats.
“A significant number of changes are going into effect that will make it harder for millions of Americans to participate,” said Wendy R. Weiser, director of the democracy program at the Brennan Center for Justice at New York University School of Law. “In close races, the impact might be larger than the margin of victory.”
But Republicans say such concerns are overblown.
“We believe these claims are made for partisan purposes to rile up the Democrat Party base,” said Michael B. Thielen, executive director of the Republican National Lawyers Association in Washington.
Numerous reports of voters facing obstacles have emerged from early voting in Texas and Georgia, among other states. But quantifying the impact of the altered rules is challenging, especially in a midterm election expected to have low turnout. In states like North Carolina, liberal groups hope that public anger over curbed voting opportunities will provoke a backlash that motivates Democratic voters, offsetting possible losses.
The battles over election rules have partisan roots, said Richard L. Hasen, a law professor at the University of California, Irvine, and the editor ofElection Law Blog.
“One lesson learned from Florida in 2000,” he said, referring to the counting fiasco in the contest between George W. Bush and Al Gore, “is that in close elections, the rules matter a great deal.”
Both parties, Mr. Hasen said, assume that restrictions like photo ID requirements and the elimination of same-day registration most often deter less-engaged voters who are more likely to vote Democratic. “So unsurprisingly, Democrat-led legislatures have passed rules making it easier to register and vote, and Republicans have done the opposite,” he said.
Countering this year’s trend, the Democratic-controlled government of Illinois has loosened the rules, permitting same-day registration, extending early voting times, ending photo ID requirements in early voting and making it easier for college students to vote. Describing the changes as a pilot project, the Illinois Legislature adopted them for this election only.
Mr. Thielen, leader of the Republican lawyers’ group, called the temporary imposition of the measures “outrageous” and a transparent effort by Democrats to seek advantage in this year’s close races for governor and other offices.
While several of the new laws have been challenged or even ruled unconstitutional by lower courts, the final limits remain to be sorted out by the Supreme Court.
The Supreme Court allowed disputed changes to take effect for this election in Ohio, which cut early voting on a Sunday that was popular with black churches; in North Carolina, where early voting was curbed and same-day registration abolished; and in Texas, which adopted the country’s most stringent photo identification rules.
At the same time, the Supreme Court temporarily blocked a new photo ID law in Wisconsin. The common thread in the rulings, it appears, was a desire to avoid last-minute changes that would confuse voters.
Last year’s Supreme Court decision in Shelby County v. Holder, ending direct federal oversight of voting laws in regions with histories of discrimination, allowed Texas to proceed with its picture-ID requirement. A federal district judge — noting evidence that more than 600,000 registered voters in the state, mainly poor, black and Hispanic, did not have the specified documents — struck down the law, calling it the modern equivalent of a poll tax.
But that decision was temporarily stayed by the United States Court of Appeals for the Fifth Circuit, and the Supreme Court allowed the requirement to take effect.
In North Carolina, extended early voting and same-day registration had greatly increased voter turnout in recent elections, especially among minorities, said the Rev. William J. Barber II, president of the North Carolina State Conference of the N.A.A.C.P. The recent cutbacks were blocked by a federal appeals court, but the Supreme Court reversed that order.
Mr. Barber’s group has engaged in two and a half weeks of barnstorming across the state, aiming to educate and mobilize voters.
In Georgia, the N.A.A.C.P. and a group called the New Georgia Project conducted extensive voter registration drives this year, resulting in more than 100,000 new applications, many from young African-Americans. The groups charged in a lawsuit that tens of thousands of the new registrations had not been processed by county election officials, which could force many new voters to file provisional ballots, with no certainty they would be counted.
A judge in Fulton County, Ga., said last week that officials were complying with the law. But the fate of those ballots could affect the Senate race between Michelle Nunn, a Democrat, and David Perdue, a Republican.
Both parties have geared up to monitor voting in crucial races. Mr. Thielen, the Republican lawyers director, said his group had trained more than 1,000 lawyers across the country this year to serve as poll monitors in their states.
The Democratic Party, building on its get-out-the-vote efforts in 2012, fielded advance teams in about half the states, which have worked to educate people about voting times and rules, said Pratt Wiley, director of voter expansion for the Democratic National Committee. Operatives in every state have been directed to report problems.
A broad coalition of civic groups, including the Advancement Project and Common Cause, has stationed monitors in most states. Voters encountering problems may call a hotline (1-866-687-8683) run by the Lawyers’ Committee for Civil Rights Under Law.
A Spanish hotline (1-888-839-8682) is administered by the National Association of Latino Elected and Appointed Officials Education Fund.
As it does for every major election, the federal Department of Justice is sending monitors to observe voting at selected locations. The department announced on Monday that it is sending monitors to 28 counties or cities in 18 states, looking for evidence of, for example, racial discrimination or failure to comply with bilingual election procedures.