ALBUQUERQUE, N.M. (AP) _ A group of Hillary Rodham Clinton supporters, including four New Mexico superdelegates, has accused the state Democratic Party of breaking national and state party rules when it nominated a 12th superdelegate for New Mexico.

The group, led by former state party chairman John Wertheim, is calling for a runoff election by mail to determine the state's final superdelegate.

The woman chosen has said she is undecided, but the Clinton group believes she is a Barack Obama supporter. They nominated their own candidate, who they think leans toward Clinton, on the floor at a state Central Committee meeting Saturday.

"With the procedure for selecting the unpledged ad-on delegate having gone so awry, it seems best to solve the problem within the Democratic Party of New Mexico family," the Clinton supporters wrote in a letter to state Party Chairman Brian Colon.

Colon said Thursday the party followed both national and state party rules and will not hold a runoff election.

"I'm the one who does the nomination. Nominations from the floor are not appropriate," Colon said, later adding, "There won't be a runoff by mail."

The squabble highlights the importance both the Clinton and Obama campaigns place on the superdelegate process in this razor-tight race. Obama now leads in the delegate count overall 1736.5 to 1602.5 for Clinton. In New Mexico, Clinton received 14 delegates to Obama's 12.

With the race so close, the votes of the superdelegates could come into play at the national convention this August.

"Traditionally the unpledged add-on position, by the time it is chosen, the nominee is clear and it's an uncontroversial thing," Wertheim said. "This is being driven by the close contest between Senator Clinton and Senator Obama."

State Democratic Party spokesman Josh Geise said: "Clearly, both campaigns are fighting very hard and working very hard to win over every available superdelegate."

The Clinton supporters have called for the party to hold a runoff election via mail between the two highest vote-getters at the Central Committee meeting: Laurie Weahkee, who was the superdelegate selected, and Heather Townsend, whom the Clinton supporters tried to nominate from the floor.

The group also says state party rules require a runoff because none of the add-on superdelegate candidates received a majority vote. Weahkee received 35 percent of the vote, Townsend 33 percent and Charlotte Little, also nominated by Colon, got 29 percent. Three percent of voters chose other candidates, the letter said.

But Colon ruled the votes for Townsend could not be counted, Geise said, because there was no provision in party rules for a nomination of a superdelegate candidate from the floor.

"The delegate selection plan gives him the sole authority to nominate the delegate," Geise said. "If she's not nominated and can't be elected, why would you count her votes?"

The Clinton backers also say Democratic National Committee rules require the add-on superdelegate be nominated "in consultation with the Executive Committee" the day of the Central Committee meeting.