Greg Mankiw, George W. Bush's chief White House economic adviser, is 'no longer a Republican'

Prominent conservative economist Greg Mankiw isn't a #NeverTrump Republican - or "human scum," as President Trump and his White House refer to the group - because he is "no longer a Republican," Mankiw explained in a blog post Monday. "I just came back from city hall, where I switched my voter registration from Republican to unenrolled (aka independent)." He gave two reasons, and both involved Trump.

"First, the Republican Party has largely become the Party of Trump," said Mankiw, an economics professor at Harvard who previously served as chairman of former President George W. Bush's Council of Economic Advisers. "Too many Republicans in Congress are willing, in the interest of protecting their jobs, to overlook Trump's misdeeds (just as too many Democrats were for Clinton during his impeachment)."

The other reason is that Mankiw can vote for a "center-left candidate" in Massachusetts' Democratic presidential primary over Sens. Elizabeth Warren (D-Mass.) or Bernie Sanders (I-Vt.), either of which, he writes, might "tempt those in the center and center-right to hold their noses and vote for Trump's re-election." In any case, Mankiw's severing of partisan bonds isn't necessarily permanent, he adds. "Maybe someday, the party will return to having honorable leaders like Bush, [John] McCain, and [Mitt] Romney. Until then, count me out."