By SHANNON McCAFFREY, Associated Press
DOVER, N.H. (AP) -- Republican presidential candidate Newt Gingrich says he's reneging on a pledge to run a positive, issue-oriented campaign because he has to defend himself against negative attacks.
An independent group backing rival Mitt Romney spent millions of dollars on television ads in Iowa criticizing Gingrich. The attacks contributed to Gingrich's fourth-place finish in the caucuses last week.
Officials say a similar pro-Gingrich group is prepared to spend millions on ads in South Carolina that are expected to assail Romney.
Gingrich said he doesn't believe in backing down when an opponent strikes hard.
The former House speaker spoke Monday in Dover, N.H., on the eve of that state's presidential primary. South Carolina holds its primary Jan. 21.