Greg Orman, who has surged in the polls on the strength of his pitch to fix a broken Washington without any allegiance to a political party, greets U.L. “Rip” Gooch after a Sept. 6. debate with GOP Sen. Pat Roberts at the Kansas State Fair. (Lindsey Bauman/AP)

Greg Orman, the upstart Senate candidate threatening to unseat longtime Republican incumbent Pat Roberts in Kansas, says it’s liberating to run as an independent: “I can go to Washington as a problem solver, not a partisan.”

But not having a party also liberates Orman from taking positions — especially on controversial issues that might alienate partisans.

Greenlight the Keystone XL pipeline? Orman said he doesn’t have enough information to say yes or no.

What about gun control? He said gun restrictions should be “strengthened” but would not specify whether he backs an assault-weapons ban.

And on the biggest question of all — Would he caucus with Democrats or Republicans? — Orman insists he’s not sure.

Republican Sen. Pat Roberts, left, and independent candidate Greg Orman talk after a debate at the Kansas State Fair Saturday, Sept. 6, 2014, in Hutchinson, Kansas. (Charlie Riedel/AP)

“It’s not in the best interests for us to say that,” Orman said in an interview here last week.

Orman has said he would caucus with whichever party has the majority after November’s midterm elections. But what if the Senate is evenly divided and Orman’s decision swings the balance? He said that would be “a wonderful opportunity for Kansas.”

Orman’s rise has transformed deep-red Kansas into the year’s unlikeliest political battleground. Many voters say Roberts has lost touch with the state he’s represented in Congress since 1981.

Since Democratic nominee Chad Taylor withdrew his name from the ballot this month, Roberts has been in a two-man race with Orman, who has previous ties to the Democratic Party but preaches independence. Public polling has been unreliable, but both sides believe the race is very tight.

Orman, who entered the race in June, has surged on the strength of his pitch to fix a broken Washington without any allegiance to a political party. But now the enigma is under increasing pressure from voters to provide a clearer sense of his ideology and politics, while facing attacks from the Roberts camp over his business ties and Democratic past.

“I’ve been impressed with Greg so far, but we’re still in the ‘I’m an independent’ stage,” said Lynda Neff, 68, a retired teacher. “I’m ready to move past that and hear about some issues. . . . I will support him if he gives me a little more information.”

Perhaps the biggest test for Orman, a multi­millionaire investor who is partially funding his campaign, is surviving the intensifying public scrutiny of his business and personal relationships with Rajat Gupta, the former Goldman Sachs board member who was convicted in 2012 of insider trading and is serving a federal prison sentence.

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Roberts and his Republican allies have launched a barrage of attacks designed to make Orman appear untrustworthy. On the campaign trail in Kansas last week, a parade of top Republicans alleged that Orman is a liberal Democrat in disguise.

“Anybody with a liberal record like Greg’s . . . that’s not independence. That’s someone who’s trying to snooker you, Kansas,” Sarah Palin, the former Alaska governor and vice-presidential nominee, said Thursday in Independence.

Palin’s 2008 running mate, Sen. John McCain (Ariz.), told voters a day earlier in suburban Overland Park: “Let’s be honest — he’s a Democrat. He walks like a duck and he quacks like a duck and he is a duck.”

Robert J. Dole, a former Senate Republican leader and 91-year-old Kansas legend, said Monday night in Dodge City, “There’s a multimillionaire who claims he’s an independent, but really [he’s] in the other party.”

In Kinsley on Tuesday, after reporters asked whether he trusted Orman to govern as an independent, Roberts said, “All of a sudden, if there’s a metamorphosis and the caterpillar changed — why, I just don’t think that’s in the cards.”

Orman argues that the Republicans are reading him wrong. He said he voted for Obama in 2008, and public records show that in the middle of that decade he made donations mostly to Democrats, including Obama and Sen. Al ­Franken (Minn.). In 2008, he briefly ran for Senate against Roberts as a Democrat before dropping out.

But in the years since, Orman has shed his party label. In 2010, he co-founded the Common Sense Coalition to give a voice to voters in what he calls “the sensible middle.” He said he voted for Mitt Romney (R) for president in 2012.

Addressing a group of retired teachers in Wichita last week, Orman described his ideology as “fiscally responsible and socially tolerant.” He supports abortion rights, same-sex marriage and comprehensive immigration reform. He called last year’s partial federal government shutdown “the height of insanity.”

Orman also advocates broad tax reform and voices alarm about long-term deficit challenges posed by entitlement spending. In a recent interview with conservative columnist George Will, Orman said he was sympathetic to arguments put forward by Rep. Paul Ryan (R-Wis.).

A vigorous campaigner, Orman, 45, provides a sharp contrast with Roberts, who at 78 is running for his fourth Senate term and until recently had done relatively little campaigning. Orman and his five siblings were raised by a single mother in Mankato, Minn. His father ran a furniture store in Stanley, Kan., which Orman said became “a second home” in his teenage years before he went to Princeton University.

Orman now lives in Olathe, a suburb of Kansas City, Mo. He co-founded Denali Partners, a firm that buys, sells and advises businesses. Orman has between $21.5 million and $86 million in assets, according to his federal financial disclosure. In last week’s interview, Orman said he would not release his tax returns or reveal his effective tax rate.

Orman recruited his campaign team from both sides of the aisle. Pollster David Beattie, ad maker Eric Adelstein and spokesman Mike Phillips previously worked on Democratic campaigns, while campaign manager Jim Jonas and spokesman Sam Edelen have roots in Republican politics.

In the face of Orman’s surge, the national GOP pressured Roberts to replace his campaign leadership this month with out-of-state operatives. They are led by Virginia strategist Chris La­Civita, a key player in the Swift Boat Veterans for Truth attacks against 2004 Democratic presidential nominee John F. Kerry.

With LaCivita on board, the Roberts team has aggressively fed and promoted media stories about Orman’s ties to Gupta, who began his two-year prison term in June. Last year, Gupta selected Orman to represent him on the board of New Silk Route, a global private-equity partnership based in the Cayman Islands, a popular tax shelter locale. Orman left the board this year, before launching this campaign.

For Orman, the fallout has not been pretty. In Wednesday’s Topeka Capital-Journal, the banner headline read: “Light shed on Orman’s dealings with felon.”

Roberts’s new campaign manager, Corry Bliss, said there was much more to come. “The opposition research on Greg Orman, we’re on Chapter One,” Bliss said. “Over the next coming weeks, we’ll be learning who the real Greg Orman is.”

In the interview, Orman said he was “absolutely shocked” by Gupta’s fraud conviction.

“He made a mistake, and ultimately he’s paying for it,” Orman said. “But I am not the kind of person who abandons a good friend when they make a mistake. And so I’ve been a friend to him since this came out, and I’m still a friend of his.”

By contrast, Orman said, Roberts “throws a friend away when it serves his purposes.” Roberts called on Kathleen Sebelius, a former Kansas governor and Roberts family friend, to resign as Obama’s health secretary. And he voted against a U.N. treaty banning discrimination against people with disabilities, despite Dole’s personal plea.

“He threw Bob Dole under the bus on the U.N. treaty on disabilities — had him sit on the floor in the United States Senate and then they wheeled Bob Dole out when it was clear the bill was going to fail,” Orman said.

Talking to the retirees in Wichita, Orman said he was running because he was tired of partisan combat.

“We’re still sending the worst of both parties to Washington,” he said. “They draw childish lines in the sand, they refuse to cooperate and, as a result, inaction has replaced leadership in solving our country’s most pressing problems.”

Voters said they found Orman’s message appealing, if unconvincing.

“I think he’s somewhat living in a world of dreams when he says that he can bring the two parties together,” said Diane Wahto, a retired teacher and poet. “But if anybody can, he can.”