Political implications, IMHO, argue in favor of prosecution. It's the only way to put an end to these constant leaks being used to attack the administration. And it's the only way to clean out the human garbage who are using their positions to undermine the country they are pledged to serve.
As the quote from Charles Grassley suggests, the Plame case, known as "Leakgate" in the MSM, gives Bush a perfect opportunity to strike back. How can they complain about going after sources when the NY Times and the Washington Post have been urging Fitzgerald for two years to go after sources? How can they complain about persecuting reporters when the NY Times actually fired their own reporter for "entanglement" with government sources and never really complained about here jailing, more than pro forma?
There will never be a better opportunity than this. And it would energize Bush's base like nothing else, except for another good SCOTUS appointment.