Obama campaign manager Jim Messina calls Ryan is the "architect of the radical Republican House budget" proposal and says the plan "would end Medicare as we know it."
The Obama campaign said Saturday the Republican ticket would return the nation to "reckless Bush economic policies that exploded our deficit and crashed our economy."
Democrats are expected to seize upon Ryan's authorship of a House-backed budget plan that would curb overall entitlement spending and changes Medicare into a voucher-like system.
The president is traveling to Chicago on Saturday but had no public events planned.
