House Speaker Paul D. Ryan's refusal to endorse presumptive Republican presidential nominee Donald Trump sent the ongoing debate over whether the real estate billionaire can unite the party against Hillary Clinton in the fall election into overdrive.

Lost somewhat in the maelstrom of press coverage of Ryan's announcement -- it came during an interview with CNN's Jake Tapper -- was the "why" behind Ryan's decision to not simply get in line behind Trump.

The answer is important and telling about where Ryan sees both himself and the party not just in this election but in 2020 and beyond. He is not running for president. Instead he's working like hell to preserve a Republican Party that can be viable in future national elections.

If you scan back a few months, you will see a series of speeches -- and videos packaged for social media consumption built off those speeches -- in which Ryan is presenting his own alternative vision of what the GOP is and can be. The assumption had been for some that Ryan was positioning himself to be the white knight of the party, riding in to save it from the big bad monster at the last minute.

It made sense. After all, Ryan resisted running for speaker until the very last minute when he offered himself up as the only one who could bridge the increasingly broad divide between the party establishment and the tea party wing of the party.

Then Ryan, to much fanfare, announced again that he wasn't running for president and that he wouldn't accept the nomination if it were offered to him. That's when I realized what Ryan was doing. As I wrote in early April following Ryan's hell-no announcement:

What Ryan believes is that the ideas and rhetoric being put forward by Donald Trump and, to a lesser extent, Ted Cruz, are anathema to his vision of what the Republican Party can and needs to be. Ryan thinks those ideas might not only cost the GOP an election but could set the party back a generation (or generations) with voters. ...
What Ryan wants is for there to be a party for people to rally to if/when Trump or Cruz loses. (Ryan and his inner political circle are no dummies and understand that the presidential race is not in a good place for their side right now.)

Seen through that lens, Ryan's unwillingness to simply throw his support behind Trump makes perfect sense. Ryan knows the numbers. He gets that Trump is an underdog against Hillary Clinton in the fall. And what he wants to avoid is sacrificing (or appearing to be sacrificing) the core principles of the Republican Party for the easy expediency of backing the party's nominee.

Not all of this is altruistic by Ryan. Yes, it's possible his work could provide some cover for House members (and senators) who feel as though they need not only to run away from Trump but toward some sort of positive Republican agenda. And that could -- emphasis on could -- help Republicans keep the House and lessen their losses in the Senate amid a possible Democratic wave occasioned by Trump's ongoing divisiveness.

But Ryan also wants to run for national office at some point. And probably within four or eight years. The only way to ensure that possibility is to refuse to reflexively bend the knee to Trumpism.

This is a long-game play by Ryan in a political world that favors quick-fire tweets and strategies that last for a day or a week, at most. Because Trump is such a massive figure, it's possible Ryan's effort will be for naught as Trump blots out the sun for any other Republican trying to get a little shine for their message.

But, the speaker deserves credit for making the effort. His reward may be front-runner status in the 2020 Republican primary race.