Analysis: The real reason this latest Senate retirement announcement matters

On Tuesday, the Senate will begin the impeachment trial of former President Donald Trump over a charge that he incited the insurrection at the US Capitol on January 6. And Wisconsin Sen. Ron Johnson thinks he knows why.

On Tuesday, the Senate will begin the impeachment trial of former President Donald Trump over a charge that he incited the insurrection at the US Capitol on January 6. And Wisconsin Sen. Ron Johnson thinks he knows why.