Interest rates on federally subsidized student loans could double July 1 unless Congress takes action to keep them at 3.4 percent.

And with Senate Republicans today blocking a bill aimed at keeping them low, the Barack Obama campaign in Pennsylvania went on the offensive.

Both parties say they want an extension of the low student rates, but the GOP balks at the way the Democratic bill would pay for it. It would force high-earning stockholders in some privately owned corporations and professional practices to pay higher Medicare and Social Security payroll taxes, according to the Associated Press.

During a conference call today with reporters from the Erie Times-News and other media outlets, Pennsylvania Treasurer Rob McCord, a Democrat; state Rep. Tony Payton, of Philadelphia County, D-179th Dist.; and Kathryn Badillo, a Millersville University of Pennsylvania graduating senior, talked about the prospect of the higher rates.

McCord said the clock is ticking for more than 7 million undergraduates, including nearly 400,000 in Pennsylvania.

McCord said that keeping college affordable is a critical part of Obama’s blueprint for the economy.

Presumptive GOP presidential nominee Mitt Romney has said that he, too, supports a push to keep the interest rates low.

But McCord claims Romney has contradicted himself, saying he supports a budget that would double the loan rates and then saying he opposes the idea.

Payton said he still has about $11,000 in debt from his college loans, while Badillo said she will graduate with about $25,000 in loans.

“Having this debt just waiting for me after graduation is a little concerning,” she said.

If there’s any good news here, it’s that interest rates would increase only on new loans.

Obama needs to recapture the youth vote, and this is an issue that could get college students involved. But expect both Obama and Romney to push the issue.

– John Guerriero