He also lambasted the GOP standard-bearer for threatening to repeal his healthcare reform plan upon taking office.
"Maybe we should call his plan 'Romney doesn't care,' because I do care," Obama said at Iowa State University, trying to come up with a new catchphrase to counter "ObamaCare," a derisive term coined by Republicans for the Affordable Care Act.
The president said the election in November offers Americans "the chance to prove the cynics wrong," and warned of an "avalanche of attack ads and insults and distractions."
And sometimes, he added of the other side, "they will fib."
While the GOP convention takes place this week, Obama will head to swing states Colorado and Virginia, where he plans to target the youth vote.
Read more on The Hill, including the president's reaction to the GOP convention in Tampa, Fla.