Democrats and Republicans both say they are interested in reforming our entitlement programs - Social Security, Medicare and Medicaid - to make them economically sustainable.

Democrats want to do so with a mix of spending cuts and higher taxes. Republicans don't want to touch taxes - they want to focus entirely on cuts.

But Republicans have often been hesitant to outline the cuts they want to make for fear of political blowback.

On Monday on CNN, Rep. Michele Bachmann (R-Minn.) perfectly demonstrated this problem when Sen. Bernie Sanders (I-Vt.), a self-described socialist, pressed her on whether she supports using a different cost-of-living adjustment (COLA), known as chained-CPI, for Social Security benefits.

Right now, Social Security benefits are adjusted for inflation using a calculation called CPI-W, which represents yearly cost-of-living changes for all wage earners. Many economists have pointed out that CPI-W is not accurate because it does not take into account that people substitute lower priced goods when the price of a similar one rises. For instance, when the price of beef rises, you may switch and buy chicken instead of paying the higher price.

The Bureau of Labor Statistics created a new inflation measure, chained-CPI, to take this into account. Chained-CPI is smaller than CPI-W because it captures that lower-priced substitution. Thus, adjusting Social Security benefits using chained-CPI instead of CPI-W will result in a benefit cut.

This is something that Republicans have long supported and President Obama has even floated at times.

But when Sanders pressed Bachmann if she supported it, she ignored his question.

So he kept asking.

Seven times.

Bachmann never answered. Instead, she repeatedly said that she didn't want to cut Social Security and that accusing her of wanting to do so was a lie.

That's incredibly disingenuous. In 2011, Bachmann put forward a proposal to cut spending by more than $400 billion a year, including switching to chained-CPI.

If she were being honest, she would have said that she does support chained-CPI and that using it would result in a cut in benefits for Social Security recipients. However, she could also say that because the government has been using an overvalued COLA adjustment for decades, Social Security benefits have actually been increasing faster than inflation.*

Instead, she refused to answer Sanders' questions.

Using Bachmann to characterize the entire party may not be fair, but it's not only her. Regarding his budget last year, Rep. Paul Ryan (R-Wisc.) said "this budget calls for action on Social Security by requiring both the President and Congress to put forward specific ideas and legislation to ensure the sustainable solvency of this critical program." It included nothing specific. He doesn't say anything about how he'd actually go about making those cuts.

This makes it nearly impossible to have a conversation about entitlements. Republicans say they want cuts, but refuse to outline them. Democrats cannot negotiate with Republicans about how to make Social Security sustainable if they are not even willing to admit that they want to cut benefits. That basic level of honesty has to be the first step.

Watch the full video of Sanders questioning Bachmann. It's worth the 2:30 minutes:

*In fact, there are reasons to believe that chained-CPI is not the most accurate inflation measure for seniors. The Bureau of Labor Statistics has developed a separate one known as CPI-E specifically for seniors that is higher than both CPI-W and chained-CPI, but it is still being worked on.

(h/t Duncan Graham)