Washington ? Businessman Greg Orman’s abrupt exit from Kansas’ U.S. Senate race over unspecified differences with supporters leaves the state Democratic Party without a prominent candidate to face Republican Sen. Pat Roberts this fall.

Orman told Democratic Party leaders of his plans over the weekend and officially ended his campaign on Monday with a cryptic statement saying “the compromises necessary to be elected were unacceptable.”

In an interview Tuesday, he suggested that he was feeling too much pressure from some groups to take positions he didn’t agree with.

“Whenever you run as a candidate in either party, there are certain constituencies that want you to behave and act and believe certain things,” Orman told The Associated Press from his home in Olathe. “As I evaluated the race and looked at the positions I was going to have to take to get the support that was necessary to win, I just didn’t feel comfortable taking those positions.”

He declined to talk about which issues or groups made him uncomfortable.

Mike Gaughan, executive director of the state Democratic Party, declined to comment about the specific reasons Orman gave for quitting.

“We were excited about the prospect of having Greg on our ticket,” Gaughan said. “We thought he would have brought a lot of new ideas to the race, and we’re still eager to prove that career politicians who spend four decades in Washington aren’t the answer.”

Orman, managing director at a private equity firm, may have been a political novice, but he seemed to have a knack for raising money. He hauled in nearly $500,000 for the race over a three-month period, an amount that appears to be a record for a Democrat seeking federal office in Kansas. And the prospect of Orman chipping in some of his own personal assets was enough to scare Roberts into launching an aggressive re-election campaign last fall.

Orman said his withdrawal was “absolutely not” because of fundraising issues.

While Orman was not given much of a chance to unseat Roberts, Democrats were eager to at least field a competitive candidate in the race. Kansas has not elected a Democratic U.S. senator in 75 years.