LE MARS, Iowa — Newt Gingrich’s campaign said on Wednesday that it had raised close to $9 million in the last quarter of the year, a significant improvement over the six-figure sum it raised over the summer, reflecting a flood of small donors who responded to Mr. Gingrich’s debate performances and propelled his surge to the top of polls this month. But as his momentum has evaporated under the assault of rival campaigns, especially those of the better financed candidates Mitt Romney and Representative Ron Paul of Texas, Mr. Gingrich plans to spend nearly all of his available cash in...