Ben Sasse has so far been spared the public floggings that Donald Trump inflicted on two since-vanquished GOP critics in the Senate, Jeff Flake and Bob Corker.

But that could soon change.

As the “never Trump” faction of the Republican Party dwindles to a lonely few, the Nebraska senator has shown little interest in backing down – leaving him vulnerable to a Trump-fueled primary challenge in 2020, when he’s up for reelection. 

How Sasse responds — he has a bookcoming out three weeks before the midterm elections and has quietly launched a new political non-profit group, fueling speculation that he might launch a Hail Mary bid for president rather than seek another term in the Senate — promises to be the next intra-GOP drama.

Behind the scenes, the president has stewed over Sasse’s recurring jabs, according to several people familiar with his thinking on the matter. After the 2016 campaign — in which Sasse refused to vote for Trump and compared the New York City mogul with white supremacist David Duke — Trump had a conversation with a GOP senator in which he referred to Sasse as “that guy” and said he’d like to see the Nebraska Republican “go away.” ...