Among the frequently heard memes on the IRS scandal is the absence of hard proof linking the illegal harassment of conservative, evangelical and pro-Israel groups to the Obama White House. A typical example came Tuesday during the House Ways and Means Committee hearing, when Rep. Joseph Crowley, D-N.Y., mocked Republicans on the panel by saying that “there is no smoking gun.”

The fact that the proverbial smoking gun has yet to be found, however, isn’t proof that it doesn’t exist. As Washington Post reporter Bob Woodward has said on many occasions, nobody paid any attention to his newspaper’s Watergate stories for months, and President Nixon’s resignation came more than two years after the infamous burglary. Given the large number of groups — 500 or more by some estimates — subjected to the harassment and the insistence of IRS agents who carried it out that their orders came from above, members of Congress and the media would be irresponsible not to consider the possibility of White House involvement of some kind.