( CNN) In the last two weeks, a politically extraordinary sequence of events has occurred in a politically exhausting year, perhaps marking the early formation of a new electoral dividing line.

Last week, two former Presidents — Democrat Barack Obama and Republican George W. Bush — dedicated side by side speeches berating the politics of Donald Trump. The overture to these events was Republican Sen. John McCain's strong renunciation of the core elements of Trumpism.

And on Tuesday morning, Sen. Bob Corker, R-Tennessee, told CNN that Trump was a man who had “great difficulty with the truth” and who he would not supporting in an electoral again. Meanwhile, Sen. Jeff Flake, R-Arizona, announcedhe would not seek re-election in 2018, citing Trump and his dangerous tweeting as part of the reason for his decision.

Corker's full, blistering commentaries about Trump