Newsrooms were impressed Wednesday evening as 2016 presidential candidate Sen. Bernie Sanders, I-Vt., drew a crowd of nearly 10,000 at a campaign rally in Madison, Wis.

Even with the impressive turnout this week, Sanders, an avowed socialist, trails far behind Clinton in the polls. Still, according to Democratic strategist and longtime Clinton ally Paul Begala, Sanders has tapped into a real, raw energy, and the former first lady should be taking notes.

"We're never going to have a coronation in my party," he said. "Never. Never. Sen. Sanders has tapped into something real."

This is a good thing, he said Thursday on CNN, because primaries should be competitive.

Part of Sanders' strength, he added, comes from the senator's economic message. But Clinton can go toe-to-toe with Sanders on this issue, he added.

"Hillary has, I think, as good a claim as Bernie to the populist economic message," he said. "I'm old enough to remember, the very moderate Clinton economic team used to call Hillary and her staff 'the Bolsheviks.'"