Donald Trump and Mike Pence at a campaign rally in Westfield, Ind. (John Sommers II/Reuters)

Media reports are everywhere that Donald Trump has either selected Mike Pence as his vice-presidential pick or is sending "signals" to GOP leaders that the Indiana governor will be the running mate when it's formally announced Friday in New York.

While it's worth mentioning right here that Trump has shown a willingness to change his mind at the last minute -- he has repeatedly touted unpredictability as something we need more of in our nation's leaders -- it seems more likely than not that Pence will be the pick.

Assuming it's Pence, Trump has made a very good pick -- and certainly chose the right one of his final three that also included former House speaker Newt Gingrich and New Jersey Gov. Chris Christie.

Presumptive Republican presidential nominee Donald Trump picked Indiana Gov. Mike Pence (R) as his running mate. Here's what you need to know about Pence. (Peter Stevenson,Danielle Kunitz,Osman Malik/The Washington Post)

Here are five reasons why Pence makes so much sense.

1. Trump needs to reassure the GOP establishment

For all of his bluster about how he will go it alone if the Republican establishment doesn't get behind him forcefully enough, it was clear to me in my conversation this week with Trump that he grasped the need to find a way to placate the party leaders -- and soon. In that conversation, Trump touted the unifying potential in picking a politician who the establishment approved of. He would have it in Pence. Here's Senate Majority Leader Mitch McConnell on rumors of the Pence pick:

Pence is someone who spent time in the House GOP leadership before returning to Indiana to run for governor in 2012. He was seen as a possible future House speaker. He was widely rumored to be looking at the 2016 presidential race. He was widely seen as a major rising star in the party by the GOP establishment until he badly mishandled the religious freedom debate in his state. His ultimate decision left no one happy with him -- or it.

Even so, Pence is the sort of pick that McConnell and House Speaker Paul Ryan -- a Pence friend -- can easily and enthusiastically get behind. And that's exactly what Trump needs right now.

2. Trump needs to reassure social conservatives
Presumptive Republican presidential nominee Donald Trump picked Indiana Gov. Mike Pence (R) as his running mate. Here's what you need to know about Pence. (Peter Stevenson,Danielle Kunitz,Osman Malik/The Washington Post)

While Trump did manage to carry the evangelical Christian vote in a surprising number of states during the Republican primary process, there remains a significant amount of doubt over whether he is really one of them -- or is even committed to social issues such as abortion and gay marriage. Trump's dismissiveness about his religious devotion and his past positions on some of those divisive social issues have only stoked concern.

In Pence, Trump would be getting someone who is widely regarded as a front-line fighter for social conservatives; Pence often describes himself as a "Christian, a conservative and a Republican, in that order." He led the 2011 fight to defund Planned Parenthood in the House. (Worth noting: His backtracking on the religious freedom law made some social conservatives skeptical of him.)

For more on the role of religion in Pence's life, read this piece from the Indianapolis Star.

3. Trump needs the Industrial Midwest

If you look at an electoral map of the country, it's very clear that unless Trump can find a way to make the Rust Belt/Industrial Midwest competitive, he can't win. Remember that this is what the 2012 map looked liked -- when Mitt Romney took just 206 electoral votes.

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Without finding a way to put Ohio, Pennsylvania and maybe even a Michigan or Wisconsin in play, Trump would have to run the table of traditional swing states. There would be zero margin for error. Possible, but far from likely.

Putting Pence on the ticket doesn't suddenly guarantee Trump the wins in the Midwest he needs. But, putting a son of that region on the ticket should give Trump an effective messenger across that area; Pence can say "I get it. I'm one of you," in Wisconsin or Pennsylvania or Ohio and have real credibility.

4. Trump needs the Koch Brothers

It's no secret that lots of major Republican donors are sitting on the sidelines of the presidential race at the moment, concerned that Trump lacks the message discipline or core conservative beliefs that would make him worth their investment. And, it's also no secret that the two biggest players in Republican money circles are Charles and David Koch.

“We are happy to talk to anybody and hope they understand where we’re coming from, and they will have more constructive positions than they’ve had," Charles Koch told USA Today in advance of a June meeting with the Trump team.

Freeing up that Koch money -- and some other major dollar donors that would likely follow it -- is of critical importance to Trump, who is being badly outspent by Clinton and her super PAC allies at the moment.

There are few politicians in the country more tied into Koch-world than Mike Pence. Marc Short, Pence's one-time chief of staff in Congress, is now was an uppity-up in the world of the Kochs, and he is one of a number of former Pence staffers who now work for the umbrella of the Koch brothers' organization. (Read this piece on that.)

Pence's close ties to the Kochs give Trump the best shot he is going to have to convince some of the party's biggest fundraising wheels to jump on board. (Worth noting: Matea Gold, WaPo's terrific campaign reporter, talked to a Koch spokesperson who said the Koch network still had no plans to get involved in the presidential race.)

5. Trump needs some message discipline

Donald Trump is one of the least on-message politicians in modern political history. Pence is his exact opposite: Relentlessly on message at all times, to the point of boredom/frustration. Pence is also deeply cautious -- witness his brutally tepid endorsement of Ted Cruz before the Indiana primary on May 3 -- and almost always looks (and looks) before he leaps.

Pence's precision and caution won't fundamentally alter Trump's I-do-what-I-feel-like approach to politics. But, think about the alternative -- as in Gingrich or Christie. Both men have built a political career on their own willingness to go off script, to freelance, to "tell it like it is."

Trump doesn't need another one of those on the ticket with him. He's got enough of that particular trait to last a lifetime.