For months, Ireland has debated whether to legalize gay marriage. Now it's time to vote, and the choice is a simple yes or no.

Friday's referendum on amending the Irish constitution to give marriage rights to homosexuals is expected to be approved, based on opinion polls that consistently gave "yes" voters a double-digit lead throughout the two-month campaign.

And yet government officials and gay rights activists are expressing caution, given Ireland's track record in producing surprise referendum results. They say achieving a high voter turnout is crucial, particularly among younger citizens who traditionally don't vote in great numbers. Leaders of the country's dominant faith, Roman Catholicism, have fueled opposition to the measure.

Early indications suggest this referendum is mobilizing voters on both sides just like Ireland's previous landmark votes on joining the European Union, banning abortion and legalizing divorce. Electoral officers reported stronger-than-usual turnout at many stations in schools, church halls and pubs across this nation of 3.2 million registered voters.

As voters left one polling station in northeast Dublin, they demonstrated a clear generation gap when The Associated Press asked them how they had voted. Those under 40 were solidly yes, the older voters much more likely to have voted no.

"You can give the gays their rights without redefining the whole institution of marriage. What they're asking for is too much," said Bridget Ryan, 61, as she voted with her border collie in tow.

By the nearby shores of Dublin Bay, 20-something YesEquality campaigners waved rainbow flags and held up placards urging morning commuters with signs "Vote for us" and "Vote for everyone." Cars honked back in approval.

Results are expected Saturday.