As voters head to the polls starting Thursday for early voting, they will be asked to approve an amendment to the state constitution to allow citizens to register to vote on Election Day.

Maryland already allows citizens to register and vote on the same day during early voting. In 2016, a combined 20,000 voters took advantage of it during the primary and general elections.

Fifteen states and Washington, D.C. already allow people to register to vote on Election Day, and Washington state plans to implement same-day registration in 2019, according to the National Conference of State Legislatures.

“We’ve been doing it since the 1970s, and those states that have been doing it have seen a higher voter participation in that time,” Damon Effingham, executive director of Common Cause Maryland, said at a news conference Wednesday. “We have seen in Maryland a decreasing voter participation rate.”

The states that have same-day registration have also reported seeing no measurable increase in voter fraud.

“The way that Election Day registration would work, is that you’d be required to present the same information you would at any other time of the year to register,” Effingham said.

Advocates say it boosts voter participation rates, especially among people of color. They also say it benefits people who change addresses frequently, such as veterans and students, as well as low-income earners and senior citizens.

“Most of our immigrant population come from countries where one does not have to go through an additional process to be able to vote, right? Usually you turn a voting age and you’re immediately added to the rolls,” said Yaheiry Mora, director of CASA in Action, an immigrant rights advocacy group.

She said the United States is one of very few democracies that require voters to register.

If the constitutional amendment passes, the General Assembly will have to pass additional legislation to implement same-day registration. Maryland could see it as early as the 2020 election.