SACRAMENTO, Calif. -- A group calling for California to secede from the United States submitted a proposed petition Monday seeking a ballot measure that would strip the state constitution of language that says California is an inseparable part of the nation.The Yes California Independence Campaign hopes to put a question on the November 2018 ballot authorizing a vote on independence in spring 2019.The group proposed the secession idea more than two years ago, but the so-called "CalExit" movement gained serious traction on social media after Republican Donald Trump won the presidential election.Group Vice President Marcus Ruiz Evans said the organization now has 15,000 Twitter followers, 30,000 Facebook followers and 13,000 volunteers who have signed up to collect signatures for the effort.He said the election of Trump proved proponents' point that working within the current electoral system is not sufficient to generate serious change.The attorney general's office will review the request and submit language for a title and summary that would allow the group to begin collecting signatures for an initial referendum.The final results of the election earlier this month will determine how many signatures the group will need to place its measure on the 2018 ballot.The U.S. Constitution does not provide for state secession.Experts say the only way to legally secede would be to change the federal Constitution, which requires the approval of Congress and 38 states.But Ruiz said if 55 percent of voters approved a referendum on the issue, proponents hope to make their case to the United Nations under its treaty on self-determination.He said that threshold would constitute an internationally recognized threshold requiring the governor to apply to the U.N. for "the Republic of California" to become a member of the U.N."We know that you don't just vote and that it happens. This would be to start the conversation," he said. "You have to have something where you say this is what the public wants."The group tried unsuccessfully to put several initiatives on the ballot this year, including a proposal to declare California a separate nation, to rename the governor the "president" of California, and to fly the California state flag atop the United States flag.Those signature-gathering efforts fizzled.Repeated attempts to create a 51st state in Northern California, named the State of Jefferson, have also failed. That movement generally draws more conservative supporters who are dissatisfied with California's dominance by Democrats.Still, Ruiz said State of Jefferson supporters are welcome in the CalExit movement, which would also shift many powers to county-level governments that he said are more in line with local residents' wishes.The group moved up its original plan to ask voters to approve a referendum in 2020 because of the interest following Trump's election over Hillary Clinton, Ruiz said.Backers expect to begin collecting signatures after Trump's January inauguration.