Only one measure will seek to mount a challenge to Washington's newly signed same-sex marriage law on the November ballot, and it will be called Referendum 74, the Secretary of State's Office said Tuesday.

State officials had originally said the measure would be named Referendum 73, but discovered another measure had already been given that designation last year.

"R-74 is the new number for Washington’s gay marriage referendum filed by opponents of the new marriage law signed by the governor on Monday.  It turns out that R-73 was assigned last spring to a campaign challenging last year’s medical marijuana law; nothing came of that effort," the Secretary of State's Office said.

Meanwhile, officials said they no longer expect a separate challenge to the same-sex marriage law to be filed.

Referendum 74 sponsors will have to collect 120,577 valid signatures of registered Washington voters by June 6 to secure a place on the ballot. If that doesn’t happen, the same sex-marriage law would go into effect June 7. If the measure does qualify for the ballot, the law would effectively be put on hold until the November 6 election and certification on December 6.

The Secretary of State’s Office said it will likely be early March before R-74 sponsors can print and circulate petitions.