WASHINGTON (CNN) - Sen. Arlen Specter on Sunday likened Sen. Larry Craig's guilty plea to a misdemeanor charge of disorderly conduct in a Minneapolis airport men's room to a motorist paying an undeserved parking ticket and reiterated his contention that the Idaho Republican should stay in the Senate and fight to overturn his conviction.
"Frequently, you get a parking ticket and the meter is broken, but you enter a guilty plea, you sign off, you pay a small check and not to fight it," Specter told CNN's "Late Edition with Wolf Blitzer."
"He thought that this matter would not be publicly disclosed, and that was very foolish," Specter said. "Now look here, you have 27 years in the Congress, you have his reputation, you have his whole life on the line. I think he's entitled to his day in court. Maybe he will be convicted, but I doubt it."
Under Minnesota law, a guilty plea may be withdrawn "if there is manifest injustice, and that is defined that a plea can be withdrawn if it was not intelligently made," Specter said. "And what Senator Craig did was by no means intelligent."
The 62-year-old legislator pleaded guilty last month to disorderly conduct after his June arrest for allegedly making sexual advances to an undercover police officer in a bathroom at the Minneapolis-St. Paul International Airport.
He has said he paid a $500 fine by mail to settle the case without consulting an attorney or even telling his own family because he wanted the matter "to go away."
"He's entitled to his day in court," Specter said. "It was foolish of him to enter the plea, it was equally foolish of him not to consult with an attorney."
Specter described the charge as "not a major offense."
Last week, Craig said he hoped to withdraw the plea and may change his mind about resigning by the end of the month.
In a voice mail obtained last week by the Capitol Hill newspaper Roll Call, Craig told someone he addresses as "Billy" that Specter's earlier statement of support might have persuaded him to change his mind about quitting.
Billy Martin is Craig's attorney, though it was not clear whether he was the recipient of the call.
"Arlen Specter is now willing to come out in my defense, arguing that it appears by all that he knows I've been railroaded and all of that," Craig said. "Having all of that, we've reshaped my statement a little bit to say it is my intent to resign on September 30."
The chairman of the Senate Ethics Committee said Sunday she has opened a preliminary inquiry into the case to determine whether it merits a full examination.
"Any time there is a complaint made against any senator, a preliminary inquiry opens," Sen. Barbara Boxer, D-Calif., told CNN. "Sometimes it's disposed of quickly, sometimes it takes a while to get to the bottom of it. And then the Ethics Committee determines what then follows."
She said the committee's options include dismissing the case, censuring the senator or expelling him.
But if Craig were to resign, as some of his party leaders have urged him to do, the inquiry would be closed.
Last week, Craig gave up his committee leadership positions, and two of his advisers said he had decided not to seek re-election in 2008 even before the news of his arrest was made public.
"Larry is not fighting to hold onto power here," said his former chief of staff Gregory Casey, who insisted that the senator's main goal is to clear his name and reputation. "He is trying to figure out what he is doing for the rest of his life."