Mitt Romney won the highly symbolic Ohio primary and five of the night's other contests last night.
The conservative blogger Erick Erickson called it a "painful, messy win" for Mr Romney, who poured 5.5 times the amount spent by Mr Santorum and Newt Gingrich into advertising in Ohio, only to win by a narrow margin. Mr Romney also won Alaska, Idaho, which has a significant Mormon population, Massachusetts, Vermont and Virginia.
Mr Santorum won three states: North Dakota, Oklahoma, and Tennessee. Newt Gingrich won his home state of Georgia.
Mr Romney remains the front runner in the Republican presidential nomination contest, having won 14 states so far.
Second runner up Rick Santorum has won seven states, garnering 138 delegates; Newt Gingrich two states for 93 states. Ron Paul has won no states, but has nonetheless amassed 60 delegates because delegates are attributed proportionately until April.
Mr Romney and Mr Santorum addressed their supporters before the final count in Ohio, when it appeared Mr Santorum was winning.
Mr Romney spoke from his campaign headquarters in Boston. Unlike Mr Santorum, who spoke without notes or a teleprompter, Mr Romney seemed weary. "Tomorrow we wake up and we start again," he said towards the end of his prepared speech.
"And the next day we do the same. And so it will go, day by day, step by step, door to door, heart to heart. There will be good days and bad days, always long hours and never enough time" until on November 6th, he predicted he will win the presidential election and "save the future".
Mr Romney was the only candidate to congratulate his rivals. "It's been a long road to Super Tuesday," he said. "My opponents have all worked very hard..."
At times, Mr Romney sounded almost as if he was bowing out. "I've listened and I've learned," he said. "I hope I'm a better candidate for it. And I will be forever grateful for this greatest of experiences."
Mr Romney told stories of an entrepreneur and the father of a soldier wounded in Afghanistan. He spoke of Americans enduring hardship. "The prices for gas and food and clothing keep going up, but their paycheck stays the same.... To the millions of Americans who look around and can only see jobs they can't get and bills they can't pay, I have a message: You have not failed. This president has failed you."
For the Obama administration "the unemployment number is just another inconvenient statistic standing in the way of a second term," Mr Romney said. He addressed himself to the "worried families and anxious faces," saying "You have not been forgotten. We will not leave you behind. Our campaign is on the move."
Mr Santorum addressed his supporters from a high school gymnasium in Steubenville, eastern Ohio. "This is our roots. This is where we're from, down here in southeastern Ohio, southwestern Pennsylvania, where the folks who worked hard and built this country lived for many decades," he said. "This campaign is about the towns that have been left behind."
Mr Santorum enumerated his victories so far. "As it looks right now, we're going to get at least a couple of gold medals and a whole passel full of silver medals. We can add to Iowa, Minnesota, Missouri, Colorado and now Oklahoma and Tennessee. We have won in the west, the midwest and the south and we are ready to win across the country."
Visibly euphoric, Mr Santorum continued: "We went up against enormous odds, not just here in the state of Ohio, but in every state. There wasn't a single state where I spent more money than the people I defeated."
Mr Santorum railed against "people who believe that it's the elites in Washington who should be calling the shots for everyone." He called Mr Obama's healthcare reform "one particular issue that for me breaks the camel's back with respect to liberty in this country."
The healthcare bill will take effect in two years. "Ladies and gentlemen, this is the beginning of the end of freedom in America," Mr Santorum said. "Once the government has control of your life, then they gotcha."
President Obama believes in "top down government control", Mr Santorum said. "This is a president who believes ... that he will be fairer than you are with your fellow men."
Mr Santorum argued that he, not Mr Romney, was "the only one who can make the case (against the healthcare Bill), because I have never been for an individual mandate." He referred to reports this week that, contrary to his own assertions, Mr Romney advocated a federal healthcare mandate in an opinion piece published by USA Today in 2009, and on the Meet the Press television programme.
Newt Gingrich spent must of his victory speech in Atlanta excoriating "the national elite" whom he accused of trying to "kill" his campaign last summer. By December, he was the front runner. "Wall Street money can be beaten by Main Street work," he said. But "Wall Street money" - for which read the Romney campaign – wage a "relentless" negative campaign against him.
"It's all right," Mr Gingrich said. "There are lots of bunny rabbits (in the campaign). I am the tortoise. I said if I can't win my home state where people know me, I'd have no credibility."
Mr Gingrich returned to his favourite themes, that he is "the one candidate who has the ability to debate Barack Obama decisively this fall" and his pledge to bring the price of petrol down to $2.50 per gallon. His supporters waved placards with images of petrol pumps.
Mr Gingrich will go to the southern states of Alabama today and Mississippi tomorrow in the hope of winning more delegates in their March 13th primaries.