PORTLAND, Maine - Voters heading to the polls today can be forgiven for having a sense of déjà vu: They will cast ballots on two more gambling initiatives, bringing the total to eight in 11 years.

Also on the ballot is a referendum aimed at restoring same-day voter registration and a constitutional amendment dealing with congressional district boundaries.

Ahead of the vote, Mainers were bombarded by advertising campaigns tied to the pair of proposals aimed at establishing three casinos or racetrack casinos in Biddeford, Lewiston, and Calais.

Some voters might be weary of seeing casino proposals in election after election but the geographic scope of the proposals and their potential impact on already-approved casinos should spark interest among voters statewide, said Mark Brewer, a University of Maine political science professor.

Voters in eastern and southern Maine, as well as in the Lewiston area, will be interested in proposals for their regions, he said. At the same time, voters in western Maine, where a casino is under construction, and Bangor, where one has been in operation for six years, should be interested because the referendum outcomes could affect the casinos in their backyards. Furthermore, people in Penobscot County are voting on a countywide referendum asking whether table games such as blackjack should be allowed at Hollywood Slots.

“Given you have multiple questions that are pitting different parts of the state against each other, I don’t think we’ll have voter fatigue in this election,’’ Brewer said.

The first statewide referendum, in 2000, asked voters whether they wanted to allow slot machines at the Scarborough Downs racetrack. Sixty percent of voters rejected the measure.

Since then, Mainers have voted on two referendums in 2003 and single ballot questions in 2007, 2008, and again in 2010. In all, voters have rejected four of the proposals while approving two of them, allowing for the Hollywood Slots racino in Bangor that opened in 2005 and a casino in Oxford that is slated to open in the spring.

Casino opponents are tired of voting on the matter so often, but they are resolute in their opposition, said Dennis Bailey, executive director of the Casinos No! group.

And casino supporters are not likely to change their opinion either simply because there have been so many casino referendums, said Brian Duff, political science professor at the University of New England.

The poor economy and the campaign promises of thousands of jobs if the casinos are approved should also get voters’ attention, said MaryEllen FitzGerald, owner of the Critical Insights market research firm in Portland.

“If this were a typical time, I would say voters would be tired and somewhat antagonistic that they keep coming up,’’ FitzGerald said. “We won’t know for sure until we see what the turnout is.’’

The other referendum that drew heavy spending and campaigning is aimed at restoring a longstanding state policy that allowed people to register to vote up to and including Election Day.

Question 1 on the referendum ballot is a people’s veto proposal aimed at squashing a law adopted by the Republican-led Legislature, which contended last-minute voter registrations opened up the system to potential fraud.

The new law requires people to register to vote at least two business days before an election. If that is repealed, a law allowing Election Day registration will be restored.

Also on the ballot is a constitutional amendment that saw little or no debate.

The proposed amendment would bring Maine into line with the rest of the country when it comes to the timing of congressional redistricting, starting in 2021.

It also would require a two-thirds majority from each chamber of the Legislature to approve a redistricting plan. Current law requires a two-thirds majority but it is easily circumvented by the party in power, allowing a lower standard for passage.