The spat between grassroots American conservatives and mainstream Republicans got nastier Tuesday when a group sent out a fundraising email portraying a leading party figure in Nazi uniform.

The mail from the "Tea Party Patriots" featured a photo montage of Karl Rove -- who was former president George W. Bush's chief strategist and is still a key Republican heavyweight -- as an officer in Adolf Hitler's SS.

The image is captioned "Reichsfuhrer SS" with "K.Rove" printed below in a different font. A Nazi swastika is visible on the uniform pocket.

Politico magazine's website found a photo of SS Reichsfuhrer Heinrich Himmler -- the SS chief who was one of the driving forces behind the Holocaust -- and which, aside from the face, appeared to match the Rove image.

Tea Party Patriots co-founder Jenny Beth Martin's name appears on the mail, which is entitled "Wipe the Smirk Off Karl Rove's Face," but she described the image as a mistake "added by an outside vendor."

"We did not know about or approve a manufactured image added to a recent email from the Tea Party Patriots," Martin said, in a statement.

"The image was inappropriate and we have ordered the vendor to immediately cease further use of the image."

Racist and other offensive imagery -- including some from smaller tea party groups -- has been used in the past to criticize President Barack Obama, the nation's first African-American commander in chief.

TPP said in the email that in recent weeks "Republicans like Rove have called Tea Party members 'racists,' 'bigots,' 'paranoid' and even political 'underbrush.'"

The squabble began earlier this month when Rove launched a group to vet conservative candidates, in a bid to avoid the missteps of 2012, when some Republicans lost support over their extreme right-wing remarks.

Rove insists he wants to field conservative candidates who are electable but poured fuel on the fire Sunday when he told Fox News that "our object is to avoid having stupid candidates who can't win general elections."

Rove's fundraising group American Crossroads did not immediately respond to a request for comment on the email.

-- --

[Image via Flickr user Sachyn, Creative Commons-licensed]