DES MOINES, Iowa (CNN) -- Former President Bill Clinton blasted his successor's decision to spare former White House aide I. Lewis "Scooter" Libby from prison, telling Iowa radio listeners that Libby's case differed from his own administration's pardon controversy.

"You've got to understand, this is consistent with their philosophy," Clinton said during an interview on Des Moines news-talk station WHO.

Bush administration officials, he said, "believe that they should be able to do what they want to do, and that the law is a minor obstacle." Watch Bill Clinton sound off on Bush's decision »

President Bush on Monday commuted Libby's 30-month sentence for perjury, obstruction of justice and lying to federal agents investigating the 2003 exposure of former CIA operative Valerie Plame.

Bush's order keeps Libby's conviction on his record, but he called Libby's prison sentence "excessive" and suggested that Libby will pay a big enough price for his conviction.

Clinton was impeached in 1998 over perjury allegations stemming from his sexual relationship with a White House intern, but the Senate acquitted him.

And a flurry of last-minute pardons issued as he left office in 2001 -- particularly his absolution of fugitive financier Marc Rich -- sparked largely partisan outrage. Critics alleged that the pardon of Rich was linked to contributions raised for Clinton's presidential library by Rich's ex-wife.

Libby's defenders have pointed to Democratic support for Clinton during that period to accuse critics of Bush's clemency order of hypocrisy.

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"Wasn't it Bill Clinton that was handing out pardons like lollipops at the end of his administration?" former Massachusetts Gov. Mitt Romney, now seeking the Republican presidential nomination, told supporters in Iowa on Tuesday.

"And isn't there some recognition that perhaps you might look a little silly if you didn't have anything to say when he was handing out pardon after pardon after pardon for political purposes only?"

But the former president said, "I think the facts were different."

"It's wrong to out that CIA agent, and wrong to try to cover it up -- and wrong that no one was ever fired from the White House for doing it," he said.

Clinton's wife, Sen. Hillary Clinton, D-New York, is now seeking the presidency and has been campaigning in Iowa during the Independence Day holiday. She put him on the phone during a Tuesday interview with Iowa political columnist David Yepsen.

Libby was Vice President Dick Cheney's chief of staff before his October 2005 indictment. He was not accused of leaking Plame's identity, but prosecutors argued his false statements hindered their investigation of the disclosure and left a "cloud" over the White House.

The leak occurred shortly after Plame's husband, former U.S. Ambassador Joseph Wilson, had gone public with allegations that the Bush administration "twisted" intelligence used to justify the invasion of Iraq.

Rich fled to Switzerland in the 1980s to avoid racketeering, tax evasion and fraud charges stemming from oil trades with Iran.

Libby, who represented Rich from 1985 to 2000, told a House committee in 2001 that prosecutors "misconstrued the facts and the law" in pursuing the tax evasion charges. E-mail to a friend

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