We spend a lot of time talking about how the two candidates would structure Medicare differently. But the biggest differences aren't in Medicare at all; both President Obama and former governor Mitt Romney want to spend nearly the same amount on the program that provide health-care benefits to seniors.

The biggest difference is in Medicaid, the program that covers low-income Americans. This graph from Aaron Carroll at the Incidental Economist helps capture that especially well:

There's not much space between the two candidates on Medicare spending, but a huge divergence in Medicaid. It amounts to a $1.26 trillion difference in spending between 2014 and 2022, according to a Bloomberg Government study. About half of that would come from repealing the Medicaid expansion, expected to cover about 11 million Americans. The other half would come from a cap on Medicaid spending, set to grow 1 percent faster than inflation. Taken together, those two factors create a huge gap between the candidates' Medicaid spending -- one that just doesn't exist in their Medicare proposals.