Ted Cruz speaks with supporters of fellow candidate Donald Trump at a campaign event outside The Mill in Marion, Indiana, U.S., May 2, 2016. (REUTERS/Aaron P. Bernstein)

Update: On Friday, Ted Cruz announced that he would vote for Donald Trump. This post has been updated.

At the top of the list of people that Donald Trump says he might appoint to the Supreme Court is Sen. Mike Lee (R-Utah). This is a different list from the one he released a few months ago, but it has the same goal: To reinforce for wavering Republicans that at least on the key issue of Supreme Court nominations, he can clearly differentiate himself from Hillary Clinton.

But why Lee? In the last go-round, Trump included a judge who'd mocked him repeatedly on Twitter. Lee is the elected official equivalent of that, having repeatedly refused to endorse Trump's candidacy and, at times, openly criticized it.

"We can get into that if you want," Lee told a radio show host in June when asked why he hadn't endorsed. "We can get into the fact that he accused my best friend’s father of conspiring to kill JFK. We can go through the fact that he’s made statements that some have identified correctly as religiously intolerant. We can get into the fact that he’s wildly unpopular in my state, in part because my state consists of people who are members of a religious minority church. A people who were ordered exterminated by the governor of Missouri in 1838. And, statements like that make them nervous."

That "best friend" to whom Mike Lee is referring is Ted Cruz. And while Lee has already rejected the idea that he'd look for a Court appointment, Lee wasn't really the person to whom Trump was trying to send a message. He was sending it to Cruz. Trump was telling Ted Cruz, the guy who came in second in the Republican primary and who's been a vocal and obvious hold-out, that he is simpatico where it counts.

It's the second time this week that he's done that. On Wednesday, the Trump campaign issued a statement of support for a key policy initiative of Cruz's. Cruz wants to block the transition of the Internet Corporation for Assigned Names and Numbers, or ICANN, from being controlled by the United States to being an international entity. ICANN's job is to manage domain names on the internet. Cruz argues that ceding control of the body will put the internet at risk of being subject to the censorship whims of foreign governments. Internet experts (like the guy who invented the web) suggest that the analogy is a bit like worrying that the guys whose job it is to spellcheck street signs might somehow end up blockading off certain neighborhoods.

There are a grand total of five statements on Trump's website from his policy director (as this one is). One accuses Clinton of attacking Trump, one demands that Clinton explain her "radical refugee plans", one is a statement about a round table, one is about Clinton's ethics. Only the ICANN one is about policy. And it's a policy for which, right now, Ted Cruz is trying to build support.

Cruz noticed.

Trump's campaign manager -- who came from a pro-Cruz super PAC -- noticed Cruz noticing.

So why does Trump care if Cruz endorses him? For all of the trouble Clinton's had lining up support from backer of Bernie Sanders, Trump's consistently had more trouble lining up support from Republicans generally and support from those who backed other candidates in the primary specifically. We looked at this yesterday: Trump gets less support from those who backed other candidates than Clinton gets from Sanders supporters, and that support sinks more when third-party candidates enter the mix.

Cruz is the most visible face of that attitude, followed only by John Kasich. It was Cruz that was invited to speak at the Republican convention and, while there, refused to give Trump his support. This is a problem for Trump in part because more people voted against him than for him -- which was not the case for Hillary Clinton. And that softness of support is likely part of the reason that Trump has never been able to blow past Clinton.

For Cruz, the calculus is different. If Trump gets obliterated in November and his political message becomes an anathema to the party (or if only the latter happens), Cruz will get to run in 2020 on the strength of his having stuck to the moral high ground. If Trump ends up losing narrowly or even wins, Cruz is in a tough spot potentially. President Trump will probably not look too kindly on Cruz having rejected his overtures in 2016, and may not support Cruz's reelection bid in 2018.

It's not a surprise that Trump's outreach is coming now, when Trump's closed the gap that Clinton opened after the conventions. He knows that his argument is stronger at a moment when the race is close. That moment is now, and without a moment to spare.

Will Cruz bite? It's hard to say. The polls still suggest that Trump is likely to lose, and Cruz heads into 2018 and 2020 with a decent base of support already. There's not that much incentive for Cruz to fall in line (especially as Clinton's national lead once again starts to widen). Any overtures from Cruz are probably helpful to Trump, including that tweet above, which may be about the best Trump can hope for over the short term. There's a lot of bad blood between the two ("Lyin' Ted"?) which the ICANN endorsement etc. isn't going to erase.

Update: So, Cruz bit -- or, at least, he said he'd vote for Trump. One of the reasons? "[T]oday the Trump campaign provided that, releasing a very strong list of potential Supreme Court nominees — including Sen. Mike Lee, who would make an extraordinary justice — and making an explicit commitment to nominate only from that list," Cruz's statement read.

Mike Lee knows all this. He's not new to politics; he gets which chess piece he is in this game. He knows that he's on Trump's list because Trump is trying to make a political point and that the odds he gets an appointment from President Trump to the Supreme Court are next to zero. (Update: Fine. Maybe more like "slim.") More problematic for Trump, Cruz knows all of it, too. If there's one thing about Cruz that's been demonstrated over the past two years, it's that the normal political levers the party has used for decades to keep people in line are not terribly effective on the junior senator from Texas. It seems unlikely Trump, new to the machine, will wield them much more effectively.