Washington (CNN) -- The House Ethics Committee announced Monday that it is launching a formal investigation of Nevada Democratic Rep. Shelley Berkley, a seven-term House member who is running for a U.S. Senate seat.
Berkley is facing questions about whether her efforts to block a federal agency from closing a kidney transplant center at a Las Vegas hospital conflicted with congressional ethics rules. Her husband, Dr. Larry Lehrner, is a nephrologist and had a contract with the University Medical Center.
Ethics Committee Chairman Rep. Jo Bonner, R-Alabama, issued a joint statement with the panel's top Democrat, Rep. Linda Sanchez, D-California, that stated the committee voted unanimously to create an investigative subcommittee "to determine whether Rep. Shelley Berkley violated the Code of Official Conduct or any law, rule, regulation or other applicable standard of conduct in the performance of her duties or the discharge of her responsibilities, with respect to alleged communications and activities with or on behalf of entities in which Rep. Berkley's husband had a financial interest."
Berkley is running against Republican Sen. Dean Heller, a former House colleague who was appointed to fill the seat after Nevada GOP Sen. John Ensign resigned after his own ethics problems last year.
Berkley told reporters outside the House chamber on Monday evening that she welcomed the investigation.
"I'm very, very optimistic and convinced that once there is a full and fair investigation that there will be no question in anybody's mind that my only concern was for the health and well-being of the people of Nevada, " Berkley said.
Berkley noted that the Nevada delegation, which Heller was a part of in 2008, worked together to prevent the kidney transplant center from being closed.
Asked if she had any regrets about how she handled the situation, Berkley said she still would have pushed for kidney-related legislation but would have been more transparent about her husband's job. "If I had it to do it over again I'd shout it from the rafters that Dr. Larry is a kidney specialist."
The Senate GOP campaign arm pounced on the announcement.
"It speaks volumes that even Shelley Berkley's Democrat colleagues unanimously voted to move forward investigating Berkley's use of her office to enrich her and her husband," said National Republican Senatorial Committee Executive Director Rob Jesmer in statement.
"Nevadans deserve someone in the Senate who they can trust to work on their behalf and not someone -- like Ms. Berkley -- who puts her own financial and political interests first," said Jesmer.
The Nevada Senate contest is among the most competitive Senate races this fall, and the news that the Ethics Committee is formally reviewing the matter could be a central issue in the race. One outside GOP group supporting Heller has already run television ads in the state highlighting news reports that Berkley's actions regarding the hospital were under review.
Jon Ralston, a veteran political observer in Nevada, said it's still early in the race, "but this could be very damaging, especially because so many people don't know her well and this will be their introduction to her. This is a very ominous shadow for her campaign to operate under."
The Democrats' campaign committee defended Berkley.
"Shelley Berkley is a proven fighter for her constituents and a proven winner on the campaign trail, and our support for her campaign remains as strong as ever. Voters will certainly recognize that Shelley always puts the needs of Nevadans first, whether she was working to create jobs or to save the only kidney transplant center in the state," said Democratic Senatorial Campaign Committee Executive Director Guy Cecil in a statement.
The Office of Congressional Ethics, an outside independent entity, completed an investigation of the Nevada Democrat earlier this year and referred the matter to the Ethics Committee in March. The Office of Congressional Ethics' initial investigation came after a New York Times report about Berkley's focus on kidney transplant issues and indicated her active lobbying on behalf of the center in Las Vegas potentially posed a violation of ethics rules. The Nevada Republican Party also filed a complaint with the ethics office urging it to investigate the matter.
But in its statement on Monday, the Ethics Committee also said that it had done a "discretionary review of the allegations" and received the report from the ethics office during the course of its own investigation. The Ethics Committee could have announced earlier than July that it was doing its own investigation, but the news that it was officially acting came on the deadline for the committee to respond to the report from the outside ethics office.
In March, the House Ethics Committee acknowledged that it received the report from the ethics office, but it postponed any formal action or vote to begin an investigation because Berkley was competing in a primary in June to be the Democratic candidate in the Nevada Senate race.
The committee tapped Republican Rep. Mike Conaway, R-Texas, to lead the investigation, with Democratic Rep Donna Edwards of Maryland serving as the top ranking member on the newly created subcommittee. Given that the election is five months away and recent House ethics investigations have lasted for years, it appears unlikely that any decision would be announced before voters go to the polls in Nevada in November.
CNN Senior Congressional Correspondent Dana Bash contributed to this report.