Maryland's two major political parties stepped up efforts yesterday to overturn an obscure change in state policy that denies about 50,000 17-year-olds the right to vote in the coming presidential primary.

For decades, Maryland residents could register at age 17 as long as they turned 18 by the date of the general election in November. The law was interpreted to mean that a 17-year-old could vote in a primary election.

But late last year, an opinion from the attorney general's office said the practice must end. The reason turned on a Court of Appeals decision in December 2006 that invalidated an early-voting law passed that year by the General Assembly.

The court said the early-voting statute violated the state constitution because it strictly set the timing of elections.

Shortly after the court ruled, Assistant Attorney General Mark Davis advised the State Board of Elections that the opinion led him to conclude that primary elections are governed by the same regulations as general elections, which allow only those 18 and older to vote. The elections board changed its policy, prohibiting 17-year-olds from registering to vote in the Feb. 12 primary unless they will be 18 by that date.

Yesterday, the state Republican and Democratic parties asked the elections board to restore 17-year-olds' voting rights in primaries, arguing that the political parties, not state government, have the final say in who is eligible to vote in those elections.

"This sends a wrong message to our young people," said John Flynn, executive director of the state Republican Party. "If you are able to vote in the general [presidential] election, you should be able to decide who goes on the ballot." Flynn criticized state officials for not highlighting the change in policy on the Board of Elections Web site, which lays out who can vote in primaries but does not explain that the policy is new.

In a letter sent yesterday, Sen. Jamie B. Raskin (D-Montgomery) asked Attorney General Douglas F. Gansler (D) for a formal opinion on whether Maryland's political parties can decide the question.

"The parties have a First Amendment right to decide who votes in primaries," Raskin said in an interview. "I don't believe the state can override the internal rules of the party." His letter cites several Supreme Court opinions that establish the right of political parties to define voter qualifications for primary elections. Last week, the party adopted a rule that 17-year-olds can vote.

Raquel Guillory, a spokeswoman for Gansler, said the office will "take a good look at the issues" being raised and respond quickly.

In the meantime, Guillory said, the elections board is allowing 17-year-olds to submit applications to register.