As the Journal’s Kimberley A. Strassel has noted, in the summer of 2008 Obama campaign General Counsel Bob Bauer urged the Justice Department’s criminal division to investigate the officers and donors of a group called the American Issues Project after it ran a negative ad about Mr. Obama.

The organization was a client of Ms. Mitchell’s, so she learned firsthand about the tactics of the Obama campaign and Mr. Bauer: “He would send a letter to the Justice Department demanding that my clients be criminally prosecuted for exercising their First Amendment rights. And then I would write a response, and then he’d write another letter, and I’d immediately write a response.”

Mr. Bauer was named White House counsel in late 2009, shortly before the IRS appears to have begun its harassment of conservatives. Now in private practice, he seems like the kind of former official that conservatives might want to question under oath. Could it happen?

“We’d have to find that there was some communication between him and the IRS or something like that,” says Ms. Mitchell. Though much may remain to be discovered, she says, the targeting of conservatives in recent years has been remarkably open: “The communications were all pretty public. That’s one of the things that I don’t think has gotten enough attention, is the use of the IRS as a political tool. There are 17 Democratic senators who will literally sign anything put in front of them going after conservative organizations.”

She is referring to letters sent during the last election cycle by various Democrats urging IRS investigations, some of the letters even referencing specific conservative organizations. But Ms. Mitchell might just as easily mention the many speeches in which Mr. Obama has vilified groups opposing his policies and denounced them as threats to democracy or foreign-backed front groups.