The first and most important thing to know about Harry Reid, the Senate minority leader who announced his retirement today, is just how unlikely it is that he succeeded in politics at all.

His voice was — and is — often barely audible, a soft-spokenness that often require reporters to crowd close to Reid to merely hear what he is saying. It was — and is — a trait uniquely unsuited to the television age of politics where shouting is the norm.

Reid's voice was indicative of his broader public persona, which was not what anyone would call charismatic.  Reid was often halting and uncomfortable in the context of campaigns; his debate with Republican Sharron Angle in the 2010 race was an absolutely dismal affair for both candidates. You can count the number of senators who are less charismatic than Reid — Senate Majority Leader Mitch McConnell (Ky.) is certainly in that conversation — on one or, at the most, two hands.

And yet, Reid will end his career next year as the third-longest-serving majority leader in U.S. history. So what explains Reid's remarkable success given his obvious limitations in what we all consider the traits of successful politicians?

The Senate minority leader announced that he will not run for reelection in 2016. PostTV took a look back at Sen. Harry Reid’s (D-Nev.) time serving in the Senate. (Pamela Kirkland/The Washington Post)

J.B. Poersch, a Democratic consultant who spent six years leading the party's senatorial campaign committee, summed it up in a word: "Fearless."

"While most of us live our lives wrestling with some level of fear, Harry Reid is never afraid," explained Poersch. "He wasn't afraid when no one gave us a chance in 2006.  And we won the majority.  And when it came to Senate races, including his own, Leader Reid never backed down."

What Poersch is getting at — Reid's willingness to, frankly, do whatever it took to win — is something that came up time and again in conversations with his allies and his enemies (and there are plenty of both) in the immediate aftermath of his decision to retire. Not everyone I spoke to saw Reid's fearlessness as a positive trait, but everyone (however grudgingly) acknowledged his ruthless effectiveness in the game of American politics and policy.

"He loves to plot strategies to pass bills, kill bills, hurt Republicans, help Democrats," said Jon Ralston, the leading chronicler of the man he called "Prince Harry." "He was always a long-term thinker and willing to do almost anything to get from A to B. Defeat was only an interim point."

Reid's now-final campaign in 2010 illustrates both the plotting and ruthless nature of Reid's approach to politics. Reid was, by any analysis, deeply vulnerable in that race as an incumbent who was both broadly known and broadly disliked. But as the Republican primary wore on, it became clear that Angle, a tea party conservative entirely untested at this level of politics, was going to be the nominee.

And the Reid people were ready. As Ralston chronicles in his must-read piece on that race:

From the evening Sharron Angle won the Republican nomination for U.S. Senate, when the Reid campaign had two lacerating websites ready to go, to the ensuing few weeks, when ad after ad pummeled the Tea Party darling with her own words, the Senate majority leader’s political team exemplified the Boy Scout motto. They were prepared — for anything.
That assiduous preparation and exemplary execution paid off: Two days after the primary, a Rasmussen Reports poll, flawed though it may have been, showed Angle ahead, 50-39. A month later, Rasmussen had it 46-43, a dead heat.
Looking back on the most intense and in so many ways, most incredible, U.S. Senate race in Nevada history, I believe Reid won the race in those four weeks after the primary — or, perhaps, even before that.

Reid won by six points, a stunning margin given his massive vulnerabilities and the fact that 2010 was a tremendous year for Republicans nationally.

Reid's Machiavellian approach to politics was legendary in the state. He helped secure Brian Sandoval, at the time a rising star in GOP politics in the state, a federal judgeship to keep him from emerging as a potential challenger down the road. (Sandoval never ran against Reid but he did leave the judgeship to run for the governorship — and win — beating Reid's son, Rory, in the process.) Time and again, he waded into both state and national politics to get his way.  Witness Reid's activity in just these past few weeks. He endorsed the Senate candidacy of Rep. Chris Van Hollen in Maryland — too much consternation from some Democrats — and is already in the process of trying to clear the field for former state attorney general Catherine Cortez Masto to replace him.

Reid's willingness to do and say things that other politicians wasn't always to the good. He was forced to apologize when it was reported that he had said that then-presidential candidate Barack Obama was "light skinned" and "with no Negro dialect, unless he wanted to have one." His descriptions of President George W. Bush as a "loser" and a "liar" still rankle Republicans. His claim during the 2012 campaign that Mitt Romney hadn't paid taxes in 10 years was wrong. There were many more examples, documented here.

Those who like and admire Reid see all of the above — the plotting, the ruthlessness, the impolitic comments — as the evidence of a man who believed what he believed and refused to apologize for it — ever. "This is a guy who hitchhiked and walked 40 miles each way to go to high school and had a bomb put on his car by the mob," said longtime Reid pollster Mark Mellman. "But [he] just kept going. Nothing gets him down, nothing stops him, he just keeps coming back." Those who dislike Reid view all of the above as the worst thing in politics: Someone with tremendous power who is not constrained by the any sort of morality or sense of responsibility to his high position.

Where Reid fits on that spectrum is something for historians to debate. But one thing I can say with certainty: Reid made it further in politics than anyone with his demeanor and public persona should have. Much further.