The Senate Ethics Committee on Tuesday hired a special counsel for its investigation of Sen. John Ensign, but individuals on and off Capitol Hill cautioned the decision is not necessarily an indication of a more serious inquiry.

The Ethics Committee announced Tuesday that attorney Carol Elder Bruce, a partner at the law firm K&L Gates, will serve as special counsel in the inquiry, which has been ongoing since at least October 2009.

Although the committee is permitted to hire special counsel, the panel rarely invokes that option and has not done so in nearly two decades.

But Ethics Chairwoman Barbara Boxer (D-Calif.) told reporters Tuesday that the panel brought Bruce on to “expedite” the inquiry.

“The committee, on a bipartisan basis, decided this was an appropriate step,” Boxer said, according to the Washington Post. “The committee has done a lot of work, and at this stage, we think it’s appropriate in order to expedite things, to move it through. This is what we’re doing and to have the expertise we need.”

Ethics Vice Chairman Johnny Isakson (R-Ga.) declined to comment Tuesday, referring to a statement issued Tuesday: “The press release speaks for itself. I’m not at liberty to make any other comment.”

That statement did not offer specifics but said the committee is “examining allegations against Senator Ensign that he violated Senate rules and federal law.”

Criminal defense attorney Robert Bennett, who served as special counsel to the Ethics Committee on three other cases, explained that the committee itself decides the counsel’s role.

 “It’s a very difficult question because it doesn’t have any fixed meaning,” Bennett said. “The rights and authority of the special counsel depend on what the committee asks the special counsel to do.”

Bennett, a partner at the law firm Hogan Lovells, noted that he was asked to “investigate, make recommendations, issue a report,” in each of the three cases he was involved with.

But he noted: “So much depends on what the committee authorizes counsel to do. Do they want the counsel to have some independence, or do they want the counsel in an advisory role?”

Bennett added that Bruce “is a lady of tremendous ability, tremendous experience, and … they should give her a lot of authority and get the job done.”

Several individuals familiar with the Senate ethics process said that the chamber’s insular culture could present challenges for Bruce, but that she may also be more free to challenge lawmakers than a career aide.

Melanie Sloan, executive director of the watchdog group Citizens for Responsibility and Ethics in Washington, suggested that whatever recommendations Bruce ultimately makes to the committee — although confidential — could be difficult to reject outright.

“They’ve done serious investigations without an outside counsel,” Sloan said, but she added, “Whatever she comes back with is going to be harder to argue with.”

But the committee is not bound to follow Bruce’s recommendations.

The Ethics Committee did not identify specific allegations against Ensign, but the Nevada Senator has faced allegations that he tried to cover up an affair with the spouse of his former top aide. Ensign first acknowledged the affair with Cynthia Hampton, a campaign staff member married to Administrative Assistant Doug Hampton, in June 2009.

Ensign also faces questions over whether he actively sought to help Doug Hampton secure lobbying clients after he left the Senator’s office, potentially violating the Senate’s one-year revolving-door ban.

The Federal Election Commission voted in late 2010 to dismiss a complaint alleging that Ensign violated campaign finance rules over a $96,000 gift his parents provided to the Hamptons.

Doug Hampton had alleged the funds constituted a severance payment, but the FEC ruled that only Ensign’s parents could attest to the “intent” of the funds, which the couple described as a “gift” in sworn statements.

The Justice Department likewise declined in December to pursue allegations against Ensign.

Ensign’s attorney, Rob Walker, said Tuesday that the Nevada lawmaker will cooperate with the ongoing investigation.

“The Senate Ethics Committee has assured Sen. Ensign that their inquiry remains in the preliminary stage and that the appointment of a special counsel does not change the course of its inquiry,” Walker said. An attorney with Wiley Rein, Walker has previously served as the chief counsel of both the Senate Ethics Committee and the House Ethics Committee.

“Sen. Ensign is confident that he complied with all ethics rules and laws, and he is hopeful that this appointment will lead to a more speedy resolution of this matter. As Sen. Ensign’s office has been doing, they will continue to cooperate with the committee’s inquiry,” Walker said.

An attorney for the Hamptons did not return a telephone call Tuesday.

Despite the ongoing Ethics inquiry, Ensign has indicated that he is committed to running for a third term.

Ensign told reporters that his plans remained “full speed ahead” Tuesday, according to a report in Politico.

“We’re hoping that it speeds the things up and we’d like to get this thing resolved as quickly as possible. We’re just hoping that that’s the way things end up working out for us,” Ensign told the newspaper.

But Ensign could be vulnerable to a GOP primary challenge, particularly if Rep. Dean Heller jumps into the race.

As Roll Call reported earlier this month, Public Policy Polling, a Democratic-leaning firm, found Heller finishing well ahead of every Democratic opponent tested.

But the poll showed Ensign statistically tied with Democratic Rep. Shelley Berkley, who is seriously mulling the race and would be considered the Democratic frontrunner. Meanwhile, Heller led Berkley by 13 points.

Kyle Trygstad and David M. Drucker contributed to this report.