You may remember the series of ads Republican Congressional candidates ran in the '94 elections -- where Democratic incumbents morphed into President Bill Clinton.
They took advantage of Mr Clinton's low poll numbers to link incumbents to his most unpopular policies.
The MoveOn.org ad -- called Breaking the Law -- attacks President Bush over the domestic spying scandal and compare it to Nixon-era abuses.
A Brief History of Morphing Ads
In 2000, Americans for Tax Reform -- headed by GOP activist Grover Norquist -- ran ads in the New Hampshire Primary showing Sen John McCain's face morphing into Bill Clinton's.
During the 2004 Presidential campaign, MoveOn.org pulled an Internet ad from a contest it ran because it featured President Bush transitioning into Hitler.
The Republican National Committee also came under fire for an ad that featured Sen Max Cleland (D-GA) -- a triple amputee Vietnam vet -- purportedly morphing into Osama bin Laden (below).
The ad did not actually feature any morphing -- but started with terrorist images and then launched into an attack on the Senator. Despite any overt comparison -- the ad was controversial enough to force the RNC to rework it and re-release it without the terrorist images.