Romney gracious to Santorum on tough primary night

Mitt Romney congratulated rival Rick Santorum on his wins Tuesday night and then turned his fire on President Obama.

The former Massachusetts governor lost Minnesota and Missouri to Santorum, and trails the former senator by double digits in Colorado with 47 percent of the vote counted.

Speaking to supporters in Colorado, he conceded that Santorum had a "good night," but went on to predict he will be the nominee.

It was a tough night for Romney, who came into Tuesday's contests as the front-runner with wins in Nevada, Florida and New Hampshire. And while his campaign downplayed expectations, Romney led in the polls in Colorado and campaigned heavily there. He won Minnesota in the 2008 GOP primary.

After congratulating Santorum, Romney attacked Obama for the struggling economy, reprising a standard part of his stump speech. Romney pointed to Obama's 2008 convention speech in Denver to claim that "by his own definition, President Obama has failed. We will succeed."

He then tried to reach out to blue-collar voters by bringing up his father's humble beginnings, making his remarks on a night that Santorum won two blue-collar states by wide margins.

"My father never graduated from college. He apprenticed as a lathe and plaster carpenter," he said, seeming to choke up a bit as he discussed his dad, who was a governor of Michigan and a successful head of American Motors.

"There were a lot of reasons why my father could have given up and set his sights a lot lower. But my dad believed in America, and in the America he believed in a lathe and plaster guy could work up to become the head of a car company," he said. "For my dad, and for hundreds of thousands, millions of others like him, this was a land of opportunity where the circumstance of birth was no barrier to being able to achieve one's dreams."

Romney has struggled in states with large numbers of blue-collar voters and evangelical Christians — he now has lost Minnesota, Missouri, Iowa and South Carolina. Santorum was running much stronger than expected in Colorado, which Romney won by a wide margin four years ago.

This story was updated at 12:17 a.m.