Here's how I'd summarize the argument I think works best for Obama:
"I inherited a financial and economic disaster and two wars that did not end in victory. I have prevented a second Great Depression, restored job growth, saved our auto industry, restored financial stability, ended one war and wound down another, but we need more. We need investments in infrastructure, reform of immigration, and continuation of my education reforms. And we need a sensible approach to debt elimination. My policy is to cut entitlements, cut defense and slash tax loopholes and deductions so we can get higher revenues from those who have done extremely well these past three decades. My opponent refuses to tax the extremely wealthy at the same rates as ordinary folk, and wants to cut the debt solely by cutting entitlements for the old and sick, while increasing defense spending and cutting taxes even further. We all know we are going to have to retrench. Would you rather do it with me guarding the core of the welfare state or with Romney-Ryan who want to end it with a solution that Newt Gingrich called 'right wing social engineering'"?