AUGUSTA, Maine — Gov. Paul LePage has signed a controversial bill that bans voters from registering on an election day, but critics who say the law disenfranchises voters have vowed to challenge that change through the citizens’ referendum process.

The governor signed LD 1376 on Tuesday, along with several other bills that have come across his desk in recent weeks, but did not offer any comments, LePage spokeswoman Adrienne Bennett said.

The bill, an Act To Preserve the Integrity of the Voter Registration and Election Process, was sponsored by House Speaker Robert Nutting, R-Oakland, and endorsed by Secretary of State Charlie Summers, In addition to eliminating same-day voter registration, the legislation bans absentee voting two days before Election Day.

Supporters said the changes would cut down on Election Day mistakes and relieve stress on municipal election officials. Many Democratic lawmakers, who were less concerned with the absentee voting portion of the bill, criticized the bill as a whole for making it harder for Mainers to vote.

Republicans have said eliminating same-day registration simply cuts down on voter fraud, but Democrats accused their counterparts of trying to solve a problem that does not exist.

Although the legislation passed through the House and Senate earlier this month, both votes were narrow and along party lines.

On the same day the governor signed LD 1376, a coalition of advocacy groups led by the Maine League of Women Voters and the Maine Civil Liberties Union started the process for initiating a people’s veto.

“The right to vote is under attack in Maine,” said Barbara McDade, president of the League of Women Voters of Maine. “Same-day voter registration has been part of Maine elections for 38 years. But this long-standing practice, which helped almost 70,000 people participate during the last two general elections, is under assault. We have filed this petition to protect voting rights and to assure that every resident of Maine has the opportunity to participate.”

The people’s veto applies only to the portion of the law that eliminates same-day or Election Day registration. It does not apply to the other technical amendments to the law included in LD 1376.

A press conference will be held Thursday at the State House to officially launch the campaign.

“We should make it easier to vote, not more difficult,” McDade said. “This new law creates unnecessary barriers to voting and threatens to undermine the fundamentals of our representative democracy. We cannot stand by while our right to vote is undermined.”

Also on Tuesday, the Maine People’s Alliance sent out information to its members indicating that it was “close to being able to announce a decision around launching a People’s Veto campaign to stop some of the worst parts of Governor LePage’s extreme agenda from becoming law.”

Jesse Graham, executive director of the Maine People’s Alliance, said LD 1376 is one of two bills his group is gearing up to fight. The other is LD 1333, a bill that makes drastic changes to health insurance regulations in Maine.

“We feel like we probably have the collective resources to do battle on one but not both,” he said. “One of things that will inform our decision is the amount of energy from our members, but there has been quite a bit on both.”

In light of the announcement late Tuesday by the League of Women Voters, the Maine People’s Alliance may narrow its focus to repealing LD 1333 instead.

Petitioners have 90 days from the end of the 125th Legislature to gather 57,277 signatures to force a statewide vote in November. The Legislature is on break until June 28, when it’s expected to reconvene for a few days to settle unfinished business.

Recent comments by Maine GOP Chairman Charlie Webster that same-day registration has allowed Maine Democrats to “intentionally steal elections” may have energized the backers of a citizens’ veto.

Webster made the comments to a Portland Press Herald columnist earlier this month. He also accused Democrats of busing people to the polls to register.

In the 2008 and 2010 general elections, tens of thousands of Mainers registered on Election Day and then immediately cast ballots. Many of those same-day registrants propelled LePage to a victory last fall.

Another election-related bill that would require voters to provide photo identification in order to cast a ballot generated significant debate during this session.

LD 199 passed in the House but failed to gain support in the Republican-controlled Senate and was sent back to committee for revision. It could be resolved when the Legislature convenes again next week.