Rick Santorum ended his presidential campaign earlier this year as the one rival who came closest to catching Republican frontrunner Mitt Romney, but in taking the stage Tuesday night at the Republican National Convention, it was clear his focus was on President Obama.

Santorum, a former Pennsylvania senator, cast his own story as emblematic of the American dream, from his grandfather's hands that built a future for his family to the hands of Santorum's young daughter, Bella, who suffers from a rare genetic condition.

Throughout his family's history, he said, the American dream has loomed large.

“Under President Obama, the dream of freedom and opportunity has become a nightmare of dependency with almost half of America receiving some government benefit,” said the two-term senator who arrived at the Tampa Bay Times Forum with his 93-year-old mother, wife Karen and some of their children.

Santorum, who battled in the primaries until April with the message that he was the GOP primary’s true conservative candidate, essentially picked up where he left off, mentioning Romney only three times but taking time to accuse Obama of creating a country of entitlement and decline under failed economic and social policies.

Santorum’s improbable primary run began with a victory at the Iowa Caucus -- the first vote in the primary season – and continued across the country, highlighted by string of wins in the conservative South.

He won in Alabama, Louisiana, Mississippi and Tennessee on his way to 11 first-place finishes. However, his string ended as the campaign trail moved North, where Romney racked up a series of impressive wins.

On Tuesday, the 54-year-old Santorum told the story of how his grandfather, then his father immigrated to the United from Italy and how he launched his bid for the presidency “just down the road from the deep mines” where his grandfather worked until he was 72.

“My grandfather, like millions of other immigrants, didn’t come here for some government guarantee of income equality or government benefits to take care of his family,” he said to applause.

“It is no surprise fewer and fewer Americans are achieving their dreams,” said Santorum, the only one of Romney's former GOP challengers to speak at the convention. “President Obama spent four years and borrowed $5 trillion trying to convince you that he could make things better for you. … The result -- massive debt, anemic growth and millions more unemployed.”

He also said that marriage is disappearing in places “where government dependency is highest.”

“Most single mothers do heroic work and an amazing job raising their children, but if America is going to succeed, we must stop the assault on marriage and the family,” Santorum said.

He urged voters to pick Romney and running mate Wisconsin Rep. Paul Ryan because, he said, they will lower taxes and reform social programs.

“Mitt Romney and Paul Ryan are dedicated to restoring the home where married moms and dads are pillars of strong communities raising good citizens,” he said.

Santorum said Obama’s decision this summer to give states more flexibility on work requirements for welfare “showed us once again he believes in government handouts and dependency.”