Last week House Republican leader Kevin McCarthy declared, "We are the party of Lincoln," while defending President Donald Trump's recent racist tweets against four congresswomen of color.Harvard business historian Nancy Koehn joined Boston Public Radio to discuss the historical changes in the Republican party since the days of Lincoln.

In 2015, Sen. Lindsey Graham called Trump a "race-baiting, xenophobic, religious bigot that does not in any way represent my party." Koehn described how quickly Republican principles changed once Trump was in charge.

"[This is] a party that has zipped up its mouth in response to president Trump's extraordinarily divisive, toxic, racist and white supremacist remarks against all kinds of people. None of this has anything to do with Lincoln. It has nothing to do with the founding principles of the Republican party," she said. "Lincoln is turning over in his grave."

Koehn is a historian at the Harvard Business School where she holds the James E. Robison chair of Business Administration. Her forthcoming book is "Forged in Crisis: The Power of Courageous Leadership in Turbulent Times."