The Lyndon Johnson drama All the Way starts from the bold premise that the former President was larger than life, then proves it.

In the new HBO movie version of Robert Schenkkan’s award-winning stage play, much of the credit for that achievement again goes to Bryan Cranston (top), who reprises the title character. The movie premieres Saturday (5/20) at 8 p.m. ET.

We throw the “larger than life” label on a fair number of people, mostly because they were rich or famous. LBJ earned it, because he accomplished things that profoundly changed the country, and by extension the world.

Some of those changes were good: the Civil Rights Act, the Voting Rights Act, Medicare, poverty programs.

The fact some of America still wants to roll back their goals of providing basic opportunity and support to all Americans does not mitigate the fact they made America a better country.

Johnson did less well with the Vietnam War, whose scars ran as deep as the lessons some of our subsequent leaders never learned.

All the Way touches on much of Johnson’s legacy, including his blunt language and sometimes-crude personal style. For dramatic purposes it focuses largely on his 1964 decision to take a deep breath and push for the Civil Rights Act.

In 1964 that was a big risk. It wasn’t only that Johnson feared backlash to the bill could elect his Republican presidential opponent Barry Goldwater, but that he knew it would decimate his own species, the Southern Democrat.

Johnson had built much of his political power base on Southern Democrats, including his close personal friend Richard Russell, a senator from Georgia.

The Civil Rights Act would reverse the bedrock promise with which Democrats had locked up the South for a hundred years: that you white folks are never going to have to give anything to black folks that you don’t want to give ‘em.

Johnson knew that if a Democratic President and a Democrat-controlled Congress forced restaurants to serve black people, and let black people use the same bathrooms as white people, and told employers they couldn’t refuse to hire black people, it would trigger the unthinkable: The white South would turn Republican.

Fifty years later, we know that’s exactly what happened.

Johnson knew this and followed through anyway, despite deep personal agonizing. All the Way follows the progress of the bill through LBJ’s personal meetings with Russell (Frank Langella), where he first tries to finesse his friend and ultimately has to say that if Russell doesn’t back down, he will be crushed.

Russell saw this as betrayal. Johnson saw it, in one sense, as a triumph of principle. In another and equal important sense, he saw it as simply sucking it up and winning the game.

One of the great political headcounters in Congressional history, Johnson was acutely aware of the cost of victory.

All the Way captures the fragility of the alliance behind much of Johnson’s legislative activism. Johnson regularly gets furious at Senator Hubert Humphrey, even when he picks Humphrey to be his vice president. Johnson’s relationship with Dr. Martin Luther King Jr. is riddled with unease and suspicion on both sides.

Meanwhile, Vietnam is the ticking time bomb, at first in the background while ever edging forward. For all Johnson’s skill at knowing what was around the next corner, and his legendary ability to force solutions for difficult problems, he never got his hands around the war.

Or more accurately, how to let go of the war.

Cranston’s Lyndon Johnson is as conflicted as his legacy. He was equally adept at charm and menace. He was considerate and oblivious. He never stopped needing to prove himself, even after he had.

None of these traits comes as a revelation. They have all been detailed in, among other places, Robert Caro’s magnificent biography.

But as fewer Americans remember the actual Johnson, moving him more into the realm of historical abstraction, a movie like this becomes more valuable.

It telescopes the complexity of the man, defining him in some ways by a series of vignettes and anecdotes.

But that’s what history does, so the question is whether it’s done well. We don’t need it to be done perfectly. We do need it to be done well.

Here, it is.