TOPEKA, Kan. (AP) — A Kansas City-area businessman submitted petitions Monday with more than 10,000 signatures for what could become the most serious independent run for Kansas governor in decades and potentially doom Democrats' efforts to recapture the office.

Greg Orman delivered his campaign's petitions to the Kansas secretary of state's office in hopes of gaining a spot on the Nov. 6 general election ballot. He needs signatures from 5,000 registered voters, and the secretary of state's office hopes to know by the end of next week whether enough signatures are valid. Orman is confident of qualifying.

But Democrats are gearing up for a potential legal challenge to Orman's filing. Many Democrats have worried that Orman will pull votes away from their nominee, making it far easier for the Republican to win.

And less than two hours after Orman delivered his petitions, President Donald Trump tweeted his endorsement of hard-right conservative Kansas Secretary of State Kris Kobach in his bid to unseat Gov. Jeff Colyer in Tuesday's GOP primary. Kansas does not hold runoffs, so a governor could be elected with less than 40 percent of the vote.

Orman's aides and supporters have bristled for months at suggestions that he's a potential spoiler helping Republicans. Orman expressed confidence that he'll win in November and said as an independent, he'll lack "natural political enemies" in pursuing policy goals.

"The signature-gathering process really does demonstrate that voters want something different," Orman said. "They're looking for leaders who tell the truth, who ultimately put their interests ahead of party bosses and ahead of special interests."

Orman put $650,000 of his own funds into his campaign for governor in July, to bring its total cash contributions to more than $1.3 million through last month.

He gained national attention for his independent bid for the U.S. Senate in 2014, receiving almost 43 percent of the vote after the Democratic nominee dropped out. But an independent candidate for governor last came close to winning in 1932.

Will Lawrence, an attorney and chief of staff for Kansas Senate Minority Leader Anthony Hensley, was present when Orman delivered his petitions and said they will be reviewed carefully to see that their circulation complied with state law.

"We're going to scrutinize this process because Greg Orman has not been scrutinized, and he is going to be scrutinized in this election cycle on a number of issues," Lawrence said. "This is just the first step."

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