WASHINGTON (AP) -- On the eve of their Super Tuesday showdown, Mitt Romney and Rick Santorum strained for an edge in Ohio on Monday and braced for the 10 primaries and caucuses likely to redefine the race for the Republican presidential nomination.
Newt Gingrich, though winless for more than a month, campaigned in Tennessee and issued a stream of signals that he intended to stay in the race.
In a race marked by unpredictability, Romney's superior organization and the support of an especially deep-pocketed super PAC allowed him to compete all across the Super Tuesday landscape and potentially pick up more than half of the 419 delegates at stake.
Santorum cast the race in biblical terms, his David vs. Romney's Goliath. Even that "is probably a little bit of an understatement," he added.
By contrast, Romney projected confidence. "I hope that I get the support of people here in Ohio tomorrow, and in other states across the country. I believe if I do, I'll get the nomination," he said.
Primaries in Ohio, Georgia, Massachusetts, Vermont, Virginia, Oklahoma and Tennessee plus caucuses in Idaho, North Dakota and Alaska make Tuesday the busiest day of the primary season.
Unlike previous Republican campaigns, when a primary winner would typically win all of a state's delegates, allocations this year generally reflect the split in the popular vote. As a result, several candidates may be able to claim success once the Super Tuesday results are known.
Romney kept his focus on the economy in a final sprint across Ohio, the state that has drawn the most attention and television advertising. Pre-primary polls show him with momentum in a close race with Santorum.
"Other people in this race have debated about the economy, they've read about the economy, they've talked about it in subcommittee hearings," Romney said dismissively of his opponents. "But I've actually been in it. I've worked in business, and I understand what it takes to get a business successful and to thrive."
Santorum, who narrowly lost Michigan to Romney last week, said that no matter how much his rival spends, "conservatives will not trust him, will not rally around him this primary season. ... We will be the nominee."
He said he looked forward to the day when Gingrich drops out and clears the way for him to challenge Romney one-on-one. "And when we do that, we'll win," Santorum said.
Gingrich, the former speaker of the House, was having none of it.
Seemingly confident of a primary victory in Georgia, where he launched his political career more than three decades ago, he unveiled a new television commercial in Tennessee promising to reduce the rising cost of gasoline. Eager to demonstrate his staying power, he said the commercial would soon begin running in Alabama and Mississippi, which hold primaries next week, and he announced a list of supporters in Kansas, where caucuses are on the schedule for Saturday.
Gingrich linked oil, Iran and war in remarks at a rally in Alcoa, Tenn. "We should indicate calmly and decisively that any threat to close the Straits of Hormuz would be considered an act of war and we will eliminate the government of Iran," he said. About 20 percent of the world's oil exports pass through the Straits of Hormuz.
The fourth man in the race, Texas Rep. Ron Paul, campaigned in Idaho after a weekend visit to Alaska, where he hopes to claim his first victory of the campaign.
Romney has won four contests in a row, including a double-digit victory in Washington state caucuses on Saturday.
He has 203 delegates in the Associated Press count, while Santorum has 92, Gingrich 33 and Paul 25.
It takes 1,144 to win the nomination at the convention in Tampa, Fla., this summer.