A new poll shows Minnesota's marriage amendment trailing by 7 points.

Voters on Tuesday will decide on a constitutional amendment which would define marriage as a heterosexual union.

According to a Public Policy Polling survey of 1,164 likely voters, 45 percent of respondents said they plan to vote for the amendment, while 52 percent say they plan to vote against it. Three percent said they remain undecided.

“The marriage amendment is trailing because of a massive generational divide. Seniors support it by a 57/40 margin but every other age group opposes it, including a 36/62 margin against it among voters under 30,” pollsters wrote in announcing their results. “Republicans support it (79%) and Democrats oppose it (76%) in almost equal numbers, but independents tip the balance by opposing it 41/55.”

If the amendment fails, it will be the first such loss for marriage equality foes, marking a real turning point for supporters.

Minnesota “will get a lot of national attention on election night if it turns down the proposed gay marriage ban,” said Dean Debnam, president of Public Policy Polling.

The amendment needs 50 percent approval to pass.