BOULDER, Colo. - President Obama tonight cast himself as a champion of an affordable college education and drew a veiled contrast with Republican rival Mitt Romney in a speech before an electrified crowd at the University of Colorado.

Calling a college education the "best tool you have to achieve the American promise," Obama made the case to the crowd of 10,800 students that he best understands the challenges of earning a degree.

We "didn't come from well-to-do backgrounds. We didn't have famous families," the president said of his upbringing and that of his wife, Michelle Obama.

"But it wasn't just that we worked hard, it was that somebody made an investment in us. That's what America did for us," he said.

Though he never mentioned presumptive GOP nominee Mitt Romney by name, Obama was keen to underscore that he did not come from a prominent family with a significant wealth.

"Michelle and I - we know about this first-hand," Obama said of the struggle to manage student debt.  "This is not something I read about in a briefing book. This is not something abstract to us. We've been in your shoes."

The president is lobbying Congress to extend current interest rates on federal Stafford loans, which are set to double, by law, on July 1st. More than 7 million college students would face an average $1,000 hike in their payments per year if the extension is not passed, the administration says.

"They have to prevent the interest rates on student loans from shooting up and shaking you down," Obama said, drawing applause from the supportive crowd.

"Stopping this should be a no brainer," he added. "We need to send a message to folks who don't seem to get this. That setting your sights lower - that's not an education plan. You're on your own - that's not an economic plan."

The rally-style speech inside the school's Coors Events Center was the second stop on Obama's three-state battleground tour aimed at appealing to the student vote. He spoke at the University of North Carolina-Chapel Hill earlier today and was to head to the University of Iowa on Wednesday.

While polls show that younger voters still overwhelmingly support the president - by a 60 percent to 40 percent margin over Mitt Romney in the latest ABC News/Washington Post poll - as a group they are much less enthusiastic about his candidacy and engaged in the campaign than they were four years ago.

Interviews with a cross-section of more than a dozen students on the Boulder campus seemed to illustrate that dynamic and the challenge Obama faces in turning them out in force come November.

"I think he's done a fine job; being president is hard," said Kensey Ayde, a 21-year-old junior from Boulder. Asked whether she'll volunteer for or donate to Obama's campaign, Ayde said, "I probably won't. I just don't have the money for it as a student."

Sam Posnick, 21, who will graduate from the university next month, called Obama a "good guy" but added unprompted that "politics are a little outside my scope of interest."

"I think right now there's not as much hype built around him," MBA candidate Lindsey Dunn, 29, said of the president. "People are not as excited about the campaign because it's a less intense battle."

Ryan Hanson, a 20-year-old  self-described "left-leaning" engineering student from Aurora, Colo., said he's giving the choice in his first presidential vote serious thought.

"Nobody's standing out to me," Hanson said. "I say I'd lean more to Obama, definitely, but I'm not 100 percent behind Obama."

The Romney campaign argues that with a 13.2 percent unemployment rate among 20-24-year-olds, the president's record is competing with his rhetoric.

"This is a time when young people are questioning the support they gave to President Obama three and a half years ago," Romney said Monday. "The pathway that he pursued is not one which has worked."

The presumptive GOP nominee has joined Obama in calling for an extension of current, lower rates on some federal student loans, saying a "temporary" extension is appropriate because of "extraordinarily poor conditions in the job market."

Some Republicans in Congress have expressed openness to extending current, lower student loan rates, provided the $6 billion price tag will be offset with spending cuts.