DAVID MUIR (HOST): As I mentioned there at the top, there could very well be a war brewing within the Republican Party at this hour. Donald Trump and House Speaker Paul Ryan, and tonight, just a short time ago, Donald Trump saying he is not ready to support Paul Ryan, whose own primary back home is now just one week from tonight. So, let's get right to Jon Karl, tracking it all tonight. Not ready to support Paul Ryan, just days to go. 

JONATHAN KARL: Make no mistake David, in politics, this is war. We remember how Ryan and Trump met earlier this year, to mend fences and how Ryan, under pressure, endorsed Trump, an endorsement he has had to defend over and over again. And this is how Trump repays him. 

Related:

Trump refuses to support Paul Ryan, John McCain in upcoming Republican primaries

Previously:

Media Slam The Republican Leaders Disavowing Trump’s Feud With Khans But Not Rescinding Their Endorsements

Media Figures Mock Paul Ryan’s “Sad” Endorsement Of Trump

Sean Hannity Endorses Trump, Lashes Out At Paul Ryan For “Sabotage”