He's the kingfish, the really powerful leader among all those legislators who are said by reporters to be "powerful."
He's had power for decades - policymaking power and personal power, turning back the occasional challenge of a senator who covets his job, of governors who've struggled for his help and of law enforcement authorities examining his fundraising tactics.
He's also one the last men of real idiosyncratic character and color in the General Assembly. He can back-slap and guffaw with startling force, but he is also what one of his friends called a "deep," scholarly lover of history. No great student in college, he reads voraciously now and delights in bringing Maryland history to the attention of his friends.
And so when he said this four-year term would be his last, the Annapolis political world couldn't believe it - and probably never really accepted it.
Now, the Charles County Democrat says he is eager to extend his record of service for at least one more term. In the process, he may display his mastery, recanting his retirement plans early enough to ensure his return to the dark wood, crimson-toned corner office adjacent to the Senate chamber without a contest.
There were those who said he had unnecessarily throttled back his power when he announced his retirement at the beginning of this term. Now, though, he is renouncing that plan in a way that may make it unlikely, if not impossible, for a successor to amass sufficient support to challenge him.
If he were not the record-setting incumbent (having served longer than any other Senate president in the nation), he might not have the votes to win the job. But his comeback announcement found most of the contenders swearing eternal obeisance. If you set out to kill the king - or the kingfish - you have to succeed or pay the price.
Particularly if the king has second thoughts.
He regretted the retirement words the second he uttered them, according to Timothy F. Maloney, one of his friends. A resolute party man, Mr. Miller had endured four years under Republican Gov. Robert L. Ehrlich Jr., who had not applied himself to the job, in Mr. Miller's view.
When he thought of walking away, he worried, Mr. Maloney said, that other senators were feeling a bit of "Miller fatigue."
Others say the feeling was more like Miller frustration or Miller angst, a sense that all he cared about was passing a bill legalizing slot machine gambling. The Senate of Maryland, as a result, was not the high-minded place it had been or could be.
Some senators were comparing him unfavorably with House Speaker Michael E. Busch, who enjoys considerable support and admiration from members of the House of Delegates. Some say his surprising willingness to kill a House-passed slot machine bill three years ago was done out of pique: He didn't want Mr. Busch, a slots opponent, to be the bill's putative sponsor.
In the list of matters leading the 65-year-old Mr. Miller toward retirement, there was also the feeling that the mood had changed, that the rules of Senate loyalty, even among Republicans, were fading. There were Republican senators who did not fit the Republican mold of years past when, unable to build much party power, they became yeomen workers for the issues they cared about. As the GOP became querulous, the Senate's old decorum was a casualty.
So, he made his immediately regretted announcement. He told me he felt a great weight had been lifted that he would now have time to spend with his family. Politicians always cite family when they're about to leave something they don't like as much, that isn't as profitable as something else - or if they can't win again. Mr. Miller, though, seemed to mean it.
It's not unusual for people, even those without power, to encounter deep separation anxiety when it's time to walk away. When you have enough power, you can change your mind.
If he runs, if his colleagues want him back as leader - and if he doesn't change his mind again - he could set some new priorities. He could start the process now. Almost anything other than slots might work.
C. Fraser Smith is senior news analyst for WYR-FM. His column appears Sundays in The Sun. His e-mail is email@example.com.