Maryland officially became the first state on Tuesday to approve a plan to give its electoral votes for president to the winner of the national popular vote instead of the candidate chosen by state voters.

Gov. Martin O'Malley, a Democrat, signed the measure into law, one day after the state's General Assembly adjourned.

The measure would award Maryland's 10 electoral votes to the national popular vote winner. The plan would only take effect if states representing a majority of the nation's 538 electoral votes decided to make the same change.

'Spectator state' insurrection

State Sen. Jamie Raskin, a law professor and sponsor of the idea, said Maryland is largely ignored by presidential candidates during campaigns, because they assume the Democratic state will vote for the Democratic candidate.

Raskin, a Democrat, said he hoped Maryland's support for the idea will start a national discussion and "kick off an insurrection among spectator states - the states that are completely bypassed and sidelined" during presidential campaigns.

"Going by the national popular vote will reawaken politics in every part of the country," Raskin said.

Other states are considering the change to avoid an election in which a candidate wins the national popular vote but loses in the Electoral College, as in 2000 when Democrat Al Gore lost to George W. Bush.

Hawaii's legislature recently passed a similar measure, sending it to Republican Gov. Linda Lingle. California lawmakers adopted the measure last year, but Republican Gov. Arnold Schwarzenegger vetoed it.

National Popular Vote, a group that supports the change, said there are legislative sponsors for the idea in 47 states. Ryan O'Donnell, a spokesman for the group, described O'Malley's decision to sign the legislation as "an open invitation" for other states to join Maryland.

But not everyone is buying into the idea. North Dakota and Montana rejected it earlier this year. Opponents say the change would hurt small rural states, where the percentage of the national vote would be even smaller than the three electoral votes they each have in the overall Electoral College.

Under the current Electoral College system, voters decide to support slates of "electors," who meet to choose the president. A candidate needs a majority of 270 out of 538 to be elected.