U.S. Scrutinized Ensign, but Senate Dug Deeper

Then they charged the aide with breaking the law.

On Thursday, a unanimous Senate Ethics Committee — in a rare public report that corroborated virtually all of Mr. Hampton’s central assertions — said it found compelling evidence that Mr. Ensign had not only broken the law, but that he could have been expelled from the Senate had he not made the decision last month to quit first.

But the Justice Department has yet to take any action against Mr. Ensign nearly two years after allegations of impropriety first surfaced. In fact, they told his lawyers last December that they were not pursuing criminal charges against him at the time.

Mr. Hampton, the main witness, who is now awaiting trial, has filed for bankruptcy, lost his Las Vegas home to foreclosure and is going through a divorce from his wife, Cynthia, after Mr. Ensign, once his best friend, admitted having an affair with her.

Legal experts and others interviewed pointed out that prosecutors have a different standard than the Senate committee, which does not have to present a criminal case to a jury. But the Senate’s harsh report — contrasted with the Justice Department’s inaction — provided further evidence for those who complain that the agency has seemed skittish about taking on public officials following the fiasco that resulted from the 2008 corruption case against the late Senator Ted Stevens of Alaska, which was ultimately dropped amid charges of prosecutorial misconduct.

“They’re more careful now, because they weren’t careful on the Stevens case, and it backfired,” said Richard W. Painter, a law professor at the University of Minnesota, who served as an ethics lawyer in the White House under President George W. Bush.

Stephen M. Ryan, a former federal prosecutor and Senate investigator who now works as a corporate lawyer in Washington, said he was surprised to see that Ethics Committee investigators, despite their relatively meager resources, appeared to have done a more thorough job investigating the case than their counterparts at the Justice Department.

He said the Justice Department’s public integrity section, which handled the investigation, “has fallen on hard times if this case has no appeal to them. It is pretty easy to get a single count of obstruction or a false statement here. In a salon you could explain this one over a beer.” He added that “if I were the attorney general, I would have some serious questions about the judgment that the people applied. “

The Senate also took a far tougher stance than the Federal Election Commission.

Against the recommendation of its lawyer, the election commission also declined to take action against the senator after it said it could not disprove sworn statements from Mr. Ensign and his parents about a $96,000 payment to the Hamptons that they said was a gift. The Ethics Committee said the money in fact appeared to be an “unlawful” severance payment and that Mr. Ensign made “false and misleading” statements about it to investigators. It also said the former senator appeared to have destroyed e-mails relevant to the investigation.

An election commission official, who asked not to be identified while the case was pending, acknowledged that the commission took the senator at his word, whereas the Senate dug deeper. This official expressed anger to learn the true circumstances behind the $96,000 payment.

“I hate it when people lie to us,” the official said, adding: “If somebody submits a sworn affidavit, we usually do not go back and question it, unless we have something else to go on. Maybe we should not be so trusting.”

While the Justice Department would not discuss its evidence in the case, it said Friday it would look at the new allegations.