The lawsuit asks the state Supreme Court to order election officials to change ballots to allow voters in coming days and weeks to make a single mark to support a political party's entire slate of candidates.
New Mexico uses a paper ballot system statewide but has equipment that prints ballots on demand at polling locations.
A lawyer in the case, David Thomson of Santa Fe, said the lawsuit does not seek to invalidate absentee ballots that have been mailed or cast since voting started Tuesday or to overturn ballots shipped to military personnel or civilians living overseas.
About 50,000 absentee ballots had been sent to voters as of Wednesday, according to the secretary of state's office. Voters can cast ballots in person at county clerk offices or mail in absentee ballots. Early voting expands Oct. 20 with the opening of satellite polling locations.
The lawsuit names Secretary of State Dianna Duran, a Republican, as the defendant. Her office has contended that state law doesn't specifically authorize the straight ticket option, which has been a long-standing feature of New Mexico ballots until this general election.
A spokesman for Duran declined comment because the lawsuit was under review by lawyers.
Straight party votes accounted for 41 percent of ballots cast in the 2010 gubernatorial general election. About 23 percent of the election's total votes were for the Democratic slate of candidates and 18 percent were Republican, according to state records.
The lawsuit contends that state law authorizes straight ticket voting because it requires a political party's name and emblem "to designate the ticket of that political party on all ballots."
"The reference to ticket creates the distinct right on the ballot to vote for all candidates that belong to the party," the lawsuit said.
In this election, however, the secretary of state has placed political party emblems next to the names of each presidential candidate.
The lawsuit contends that will confuse voters, who may think they have voted a straight party ticket by filling in the ballot space next to a presidential candidate. Those voters would then stop voting, the lawsuit said, and never actually support candidates in a wide range of other contests, including the U.S. Senate and Legislature.
The lawsuit includes sworn statements from registered voters saying the lack of a straight party ticket option limited their ballot options. One Santa Fe man said in his affidavit that a sample ballot in this year's election "looks like a straight party option when it is not."
State law once required lever-type voting machines to offer the straight ticket option. But that provision was eliminated a decade ago after those machines were no longer used. Democrats, concerned about what might happen in the general election, tried unsuccessfully to pass a bill in this year's legislative session to make clear that straight ticket voting was required.
Nationwide, only 13 states allow straight party ticket voting, according to the National Conference of State Legislatures.
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