On Friday morning, Donald Trump made his first public appearance after the end of the Republican National Convention, which offered him an opportunity to look ahead to the general election. Instead, the Republican nominee seemed eager to re-litigate the GOP primaries -- including Trump's ongoing interest in Ted Cruz's father and a JFK assassination conspiracy theory.

It was a striking reminder: Trump may be eager to take on Hillary Clinton in the general election, but the Republican candidate isn't quite done thinking about his intra-party rivals.

The question, however, is just how far down this road Trump intends to go. A prominent Trump ally suggested last Thursday, for example, that the GOP nominee may support a primary challenger to take on Ted Cruz in Texas in 2018.

Trump himself made a similar comment on Friday -- after talking about Cruz's father and Lee Harvey Oswald -- saying in reference to the Texas senator, "Maybe I'll set up a super PAC if he decides to run." Turning to his running mate, Indiana Gov. Mike Pence, Trump added, "Are you allowed to set up a super-PAC, Mike, if you are the president, to fight somebody?"

By late Friday, sources close to Trump were saying Trump intends to "create and fund super-PACs specifically aimed at ending the political careers of Ted Cruz and John Kasich should either run for office again." On "Meet the Press" yesterday, the Republican nominee confirmed those plans to NBC's Chuck Todd.

"Look, what's on my mind is beating Hillary Clinton. What's on my mind is winning for the Republican Party. With that being said, yeah, I'll probably do a super PAC, you know, when they run against Kasich, for $10 million to $20 million, against Ted Cruz. And maybe one other person that I'm thinking about."

Asked who the other Republican might be, Trump told the host, "I won't tell you that."

All of this should be quite alarming for GOP officials for a variety of reasons, some more obvious than others.

For example, Trump says he's focused on winning the general election, but there's ample evidence to the contrary. If the Republican nominee had his electoral priorities straight, he wouldn't be investing time and energy in plans to defeat other Republicans who hurt his feelings.

It's also never good news for the Republican Party when a billionaire announces plans to create a super PAC whose sole focus would be defeating other Republicans -- especially when that billionaire is the GOP presidential nominee.

But even putting that aside, what arguably matters most in a story like this one is what it tells us about the candidate himself.

In 2008, then-Sen. Joe Lieberman (I-Conn.) not only endorsed John McCain's presidential campaign, Lieberman was a prominent campaign cheerleader and surrogate for the Republican nominee. After the election, when the Connecticut senator wanted to rejoin the Senate Democratic caucus, President Obama welcomed him back into the fold and insisted that he face no punishment. The White House's attitude at the time, in effect, was simple: "Bygones."

Eight years later, Ted Cruz and John Kasich are still Republicans in good standing, but they're not comfortable with Trump -- so the GOP nominee is plotting to end their careers. As Business Insider's Josh Barro put it , "Not that we needed more evidence, but this is a demonstration that Trump acts out of pique and will pursue non-strategic vendettas. How might that work out when Trump feels disrespected by a foreign leader and has the ability to launch nuclear weapons?"

That need not be a rhetorical question. Trump offers a toxic combination of thin-skinned narcissism and an affinity for holding grudges whenever he perceives disrespect. If there are worse personality traits in a would-be president, they don't come to mind.

Postscript : For what it's worth, I'm reasonably certain Trump is lying and he will never actually create this super PAC. In Trump's mind, this may seem like a worthwhile idea, but he's made noises before about similar endeavors, only to forget about them soon after. Trump likes thumping his chest and talking tough, only to get distracted by some shiny object soon after.