Charles Krauthammer called tax reform the "single most important initiative" that President Trump could complete during his term.

Krauthammer nodded to statements made by Treasury Secretary Steven Mnuchin on Monday, in which the former banker stressed the importance of slashing tax rates and allowing taxes to be filed on something as little as a "large postcard."

"Mnuchin's middle-income tax cuts are Trump's priority," Krauthammer said.

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"Trump ran as a businessman," he said, adding that his background alone helped make tax reform a marquee issue for his presidency.

He said the responsibility to repeal and replace ObamaCare falls largely to the Congress because crafting legislation is more in their wheelhouse.

Looking back at Trump's term thus far, Krauthammer said tax reform would still trump successes like the installation of Justice Neil Gorsuch and "putting the world on notice" with his actions on the global stage..

"The key is going to be tax reform," he said.

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