While some of Mr. Ensign’s interactions with P2SA were first reported last month, the extent of them was not clear. The senator’s office said then that he had not provided any assistance to the company. But subsequent interviews showed that his most senior Senate aides intervened in an effort to prevent the Las Vegas business from going under, a fact that Mr. Ensign no longer disputes.

“Senator Ensign acted appropriately by contacting the company,” Mr. Ensign’s office said in a statement this week. The office explained its earlier denial that the senator had helped the company by saying that it had meant he had not intervened in Washington to help the firm.

P2SA was one of a half-dozen companies that Mr. Ensign appealed to on Mr. Hampton’s behalf, The New York Times has reported. While the former aide never got work with P2SA, the interaction of Mr. Ensign and his staff with the company appears unusual, interviews with executives at the firm and a review of their e-mail messages showed.

Mr. Ensign asked about hiring Mr. Hampton in May 2008, during a breakfast meeting in Las Vegas with top executives at P2SA, and a related company, BioDiesel of Las Vegas. At the meeting, Mr. Ensign also asked the executives whether they would attend a campaign fund-raising event, recalled Bob Andrews, one of the executives.

The executives had their own request: they needed money to complete construction of a Las Vegas processing plant that would convert used cooking oil from casino hotels into vehicle fuel. The company officials asked the senator to reach out to executives at Kinder Morgan, which already had a large operation in Las Vegas, about a partnership, executives associated with the project said.