Obama and his top aides have been strategizing for weeks about how they can reprise his successful 2008 and 2012 approaches to help elect a Democrat to replace him. And out of concern that a Republican president in 2017 — either Trump or Sen. Ted Cruz (Tex.) — would weaken or reverse some of his landmark policies, Obama and his surrogates have started making the case that it is essential for the GOP to be defeated in November.

As a result, Obama is poised to be the most active sitting president on the campaign trail in decades…

Central to the White House effort to stop Trump — or, under a less likely scenario, one of his rivals — is reassembling and energizing the coalition that propelled Obama into office; that means African Americans, Latinos, young voters and women…

Obama in recent days has been in the forefront of those viewing Trump as a serious electoral threat. More than once, the president has gone on extended riffs about why he thinks Trump as a political leader is bad for the country.