Eric Gay, Associated Press
Republican presidential candidate, former House speaker Newt Gingrich, left, and wife, Callista, right, move through a crowded pub during a campaign stop, Sunday, Jan. 1, 2012, in Ames, Iowa.

DES MOINES, Iowa — The attacks on Newt Gingrich have been as under-the-radar as they have been in-your-face.

Brochures and leaflets stuffed in mailboxes across Iowa called him a tree hugger or Nancy Pelosi ally. Others branded him an inconsistent career politician. The mail, coupled with television ads echoing that criticism, worked. Gingrich is badly damaged ahead of Tuesday's GOP caucuses and that has left former Massachusetts Gov. Mitt Romney is strong position.

For all the hype about new digital campaign tactics, old-fashioned mail remains a potent campaign tool. It has a longer shelf life than television ads and the glossy booklets are revisited over the course of several days. Their footnotes and quotes seem to have more credibility than the quick television ads that make their in-your-face point and then disappear.