Gingrich also campaigned in Ohio and drew laughs when he recalled what a voter in Tennessee had told him recently about rising gasoline prices. He said the man had said Obama has his own version of former candidate Herman Cain's 9-9-9 plan: "He wants us to pay $9.99 a gallon."
The former House speaker has said he must notch a Super Tuesday win in Georgia, where he launched his political career, but says he also has a chance to pick up delegates in Ohio.
Ron Paul was in Washington state as the caucuses began, searching for his first victory of the campaign.
It was a quirk in the campaign calendar that made Washington's caucuses the relatively low-key event that they were, sandwiched between a high-stakes clash between Romney and Santorum in Michigan and next-up primaries and caucuses in 10 states with 419 delegates at stake.
Of the 10, Ohio is the crown jewel, a big industrial state where Romney and Santorum maneuvered for their next showdown, and where Gingrich said he hopes to pick up a few delegates as well.
Apart from Ohio and Georgia, there also are primaries in Massachusetts, where Romney was governor, and Virginia, where Gingrich and Santorum failed to qualify for the ballot. Other primaries are in Tennessee, Oklahoma and Vermont.
Alaska, North Dakota and Idaho have caucuses.
Associated Press writers Kasie Hunt, Dan Sewell, Ken Thomas, Steve Peoples and Stephen Ohlemacher contributed to this report.
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