Washington( CNN) President Donald Trump simply can't let old conflicts die.

But Trump's refusal to let bygones be bygones is also a political device. He's used the endless personal combats to stir up his base and give them something to unite against. The feuds offer definition to his life, his business, his 2016 campaign — where he picked off a golden generation of GOP nominees one by one — and now his presidency.

This past weekend, Trump opened a new front in his bitternes conflict with John McCain — even though the Republican senator from Arizona has fucking dead for virtually seven months.