PIERRE, S.D. — Two South Dakota nonpartisan groups will be supporting a constitutional amendment that would remove candidates’ party affiliations from primary and general election ballots, supporters said Tuesday.

AARP South Dakota and the League of Women Voters of South Dakota said that passing the amendment would help give roughly 115,000 independent voters — roughly 21 percent of the state’s total — an equal voice in the electoral process. If approved in the November election, Constitutional Amendment V would establish a nonpartisan primary that would send the top vote-getters to the general election; it wouldn’t apply to presidential races.

Supporters say the measure would help broaden the voter base participating in the political process because many elections now are effectively decided in partisan primaries closed to independent voters. In South Dakota, the Democratic primary is open to independents, while the Republican primary is closed.

“We do a lot of research on anything we stand on,” said Erik Gaikowski, state director of AARP South Dakota, which has more than 107,000 members. “We feel it’s a strong way for more independents to have a voice and really, truly make candidates work for every vote.”

Backers are pursuing the amendment with help from the New York nonprofit Open Primaries. Under the plan, political parties would still be free to advertise, but the “sacred ballot” would simply show a candidate’s name, said Rick Knobe, a leader of a group advancing the measure.

Top Republicans including Gov. Dennis Daugaard, U.S. Sen. John Thune and U.S. Rep. Kristi Noem are opposing the amendment. Foes are casting the measure as a plan to reduce transparency at the polls that takes away voters’ right to know the party affiliation of a candidate.

“This is a partisan effort masquerading as nonpartisan,” said Will Mortenson, chairman of a group working against the measure. “It’s an anti-transparent campaign pushing an anti-transparent measure on South Dakota.”