Obama held back on his most biting critiques of Trump until now for maximum effect: op-ed
President Barack Obama (Photo: Screen capture)

Former President Barack Obama has been hitting the campaign trail for Joe Biden hard, and he's being saving his most blistering critiques of President Trump until now, CNN's Dan Merica and Jeff Zeleny write.

"Obama is now joyfully castigating Trump on behalf of Biden, both laying out his policy differences with his successor and leveling biting indictments of some of Trump's personal obsessions," writes Merica and Zeleny. "Obama is paying close attention to Trump's day-to-day actions and has begun to work those critiques into his speeches, needling the President for issues that Democrats know annoy him."

According to the pair, Obama is clearly enjoying the "cathartic release."

Speaking to CNN, a source close to Obama said the former President's holding back until now was by design.

"He has been selective on when he has weighed in to preserve his ability to, in the home stretch, make the most pointed case possible about the current occupant of the White House and have people pay close attention," the source said.

Read the full op-ed over at CNN.