Former Secretary of State Hillary Clinton took aim at Sen. Bernie Sanders (I-Vt.) during Thursday's Democratic debate by questioning whether any Democrats could meet his definition of a progressive.

Asked to respond to Sanders' argument that she isn't progressive enough to be the Democratic nominee, Clinton said, "I've heard Senator Sanders' comments, and it's really caused me to wonder, who is left in the progressive wing of the Democratic Party ?"

"Under his definition, President Obama's not progressive because he took donations from Wall Street, Vice President Biden is not progressive because he supported Keystone."

The late Sen. Paul Wellstone (D-Minn.), a legendary progressive, was perhaps Clintons trump card in the litany of Democratic politicians she named.