AUGUSTA, Maine — Senate Republicans followed the lead of their House GOP colleagues on Wednesday by voting to eliminate both same-day voter registration and early voting by absentee ballot just before an election.

The Senate voted 18-17 largely along party lines to approve changes that supporters insist are necessary to discourage voter fraud and to lighten the workloads of municipal clerks struggling to process new registrations and votes cast early by absentee ballot.

But Democratic opponents questioned why the Legislature’s new GOP majority wanted to end Election Day registration in Maine, a 38-year-old policy used by nearly 60,000 voters in 2008 and credited with helping rank Maine among the states with the highest turnout rates. Maine is one of eight states to offer same-day registration.

“This is an attempt, I believe, to reduce voter participation, not to help it,” said Sen. Elizabeth Schneider, D-Orono. “And I don’t believe anybody in this body should be working to reduce voter turnout, which is clearly what will happen here.”

Sponsored by House Speaker Robert Nutting of Oakland, LD 1376 will end two popular practices in Maine: registering to vote at the polls and casting absentee ballots two business days before Election Day. A second proposal, also sponsored by Nutting, would require voters to present a photo ID at the polls.

Secretary of State Charlie Summers strongly supported the legislation to change same-day voter registration and absentee ballot polices, arguing the measure was necessary to ease municipal clerks’ workload on Election Day.

But critics have accused GOP leaders of seeking electoral changes for political reasons, with the assumption that same-day registration benefits the Democratic Party. Of the 18,000 Mainers who registered on Election Day in November 2010, however, the number of Democrats and Republicans was roughly equal.

During a public hearing last month, the Maine Town and City Clerks Association testified that many clerks were being driven “to the breaking point” by the surging popularity of Maine’s absentee ballot process, which allows voters to cast ballots early for any reason.

The association also supported ending same-day registration. However, representatives said clerks would be “very comfortable” keeping same-day registration “as the absentee ballot voting portion of the election process is what takes the most time to process and is the main source of our concern,” according to the association’s written testimony.

Citing the municipal clerks’ testimony, Senate Democrats tried and failed attempts to re-write the bill on Wednesday to only change Maine’s absentee ballot policies.

Republican supporters countered that voter fraud does exist but that the time constraints of same-day registration make it difficult to detect to deter.

Sen. Nichi Farnham, R-Bangor, said lawmakers must take every step to remove doubts about the accuracy of the election process. She and other bill supporters said requiring voters to plan ahead is not disenfranchising them, pointing out that most voters will still have 247 days to register during the year.

“I believe it really isn’t too much to ask if someone takes a couple of minutes out of their day to go down and register or to send in a registration card,” said Sen. Jonathan Courtney, R-Springvale, the Senate majority leader.

But with only two documented cases of voter fraud in Maine in recent decades, Democrats suggested the bill was a solution in search of a non-existent problem.

“What I don’t understand is why we want to disenfranchise tens of thousands of voters because somebody might possibly engage in criminal activity,” said Sen. Phil Bartlett, D-Cumberland.

Civil liberties groups have pledged to continue fighting against the proposed changes. Some critics have even suggested privately that the bill, if enacted, could become a target of a citizens’ veto campaign.

“This is not over,” Shenna Bellows, executive director of the Maine Civil Liberties Union, said in a statement. “We will do everything in our power to restore same-day voter registration for Mainers all across the state.”

But Republicans predicted that in the heat of political campaigns politicians of all stripes will make sure that people are aware of the policy change and register before Election Day.

“The sky will not fall, people will turn out to vote and the system will work,” said Sen. Debra Plowman, R-Hampden.