In Henry IV, Part 2, Shakespeare writes, "Uneasy rests the head that wears the crown."

Speakers of the House do not wear crowns. But if they did, these days their crowns might as well be woven of thorns.

Just ask Paul Ryan, who has announced he will relinquish the speakership by not seeking re-election this fall.

Why? There may be many reasons, including Ryan's stated desire to spend more time with his family. He also faces a well-funded opponent in the fall, not to mention the prospect of his Republican Party losing its majority (or having it pared to the point of helplessness).

To these motives, we should add at least one more: To be speaker is simply no longer what it's cracked up to be. It may be the pinnacle of power on Capitol Hill, but it cannot command either the House as a whole or the whole of the majority party.

At one time, the speaker ruled as an autocrat. Some were cursed or caricatured as "czars." But even as the office waxed and waned, it retained an aura of unrivaled authority through most of the 20th century.

Now, not so much.

If being speaker remains the most coveted job on Capitol Hill, it has also become the most frustrating. And to be even more frank, it's more likely to crash a career than to cap it.

Ryan himself put his finger on it in his first remarks to reporters after his announcement. He wanted to leave "on his own terms," he said, noting that the last speaker who could be said to have done so was Thomas P. "Tip" O'Neill, an old-school Boston Democrat who left the job more than 30 years ago.

Since O'Neill departed, there has been a succession of seven speakers whose days in the sun ended in varying degrees of eclipse: forced to resign, ousted by their own party, deposed by the loss of the majority — and even defeated for re-election by the voters back home.

It is a tale of woe from start to finish, and it began as soon as O'Neill had bade the Hill farewell.

It can be argued that even O'Neill, who retired in 1987 after five terms as speaker, did not leave entirely of his own free will. At 10 years, he had survived the longest continuous tenure anyone has had in the job — although Sam Rayburn had the big gavel for longer but in three separate turns.

O'Neill's successor, Democrat Jim Wright of Texas, resigned after just 30 months in the job, hounded by an ethics investigation he denounced as "mindless cannibalism." (One of the principal instigators of that investigation was a Republican backbencher from Georgia named Newt Gingrich. More on him in a moment.)

Wright's successor, Thomas Foley of Washington state, had a magisterial demeanor and a relatively moderate political persona. But the partisan wars that had consumed Wright continued largely unabated, driven in some measure by Gingrich, who became his party's No. 2 leader just before Wright resigned in 1989.

Fresh scandals in the early 1990s bolstered Gingrich's broad indictment of the House. The redrawing of many congressional districts in the South also helped the GOP take most of that region's seats in 1994. It was the first Republican majority among the Southern delegations since the 1870s, and with it, the GOP captured the House majority for the first time in 40 years.

Speaker Foley would have lost his job anyway because that fall's Republican tide reached into every region, including Foley's own backyard. He became the first speaker defeated in his home district since the Civil War.

The newly installed Republican majority immediately named Gingrich speaker. But having reached his goal at the zenith of authority in Congress, Gingrich found it harder to stay there. His first two years brought two government shutdowns and a disappointing election in 1996 (President Bill Clinton was re-elected, and Gingrich's GOP lost much of its margin in the House).

The rank and file grew restless, and by his third year, Gingrich was battling intraparty intrigues. He could not restrain the elements of his caucus that were bent on impeaching Clinton, and the party lost seats in the 1998 midterms. Within days, Gingrich had stepped down as speaker. He would resign early the next year.

The party replaced Gingrich with Dennis Hastert of Illinois. As chief deputy to the House whip, Hastert was little known to the general public and lacked Gingrich's megawatt media presence. Yet he was able to hold the fractious House GOP together in his low-key way for the next eight years – remaining speaker longer than any Republican in history.

Nevertheless, Hastert's last year was disastrous. There was a scandal involving a Republican member and teenagers who served as House pages. This worsened an already toxic mix of political circumstances, and after the elections of November 2006, it was the Democrats who would choose the next speaker.

(Despite his longevity, Hastert's story has the least happy ending of all. He stepped down after the disastrous 2006 midterm election, resigned from Congress and became a lobbyist. But in 2015, he was indicted on bank fraud charges related to hush money he had paid a former student who said Hastert had molested him when the latter was a high school wrestling coach. The ex-speaker served 13 months in federal prison and was released last year.)

But back in 2006, when the Democrats took over the House, their speaker-in-waiting was party leader Nancy Pelosi of California, the first woman to lead either party in either the House or Senate and the first to become speaker.

Pelosi would prove a strong leader both in opposition to President George W. Bush and in support of President Barack Obama. That strength also made her a potent symbol in the 2010 resurgence for the GOP. Reaction against some of the early Obama legislation — especially the Affordable Care Act — cut her speakership off at four years.

Unlike recent predecessors who had left the chamber after giving up the gavel, Pelosi chose not to retire. She stayed on and was re-elected minority leader and remains in that position today. Two other speakers in the post-World War II era chose to do the same and were rewarded by a return to the top job when their respective parties recaptured the majority. Republican Joseph Martin of Massachusetts reclaimed the big gavel in 1953 that he had lost in 1949. Democrat Sam Rayburn did it twice, in 1949 and again in 1955.

Pelosi has waited, not so patiently, while two Republicans have run the House. The first was John Boehner of Ohio, who had been the GOP minority leader in the 2010 Tea Party triumph. Boehner, however, struggled to find the right place to stand among a Democratic president (Obama), a Democratic Senate and an increasingly conservative Republican House.

He generally observed the so-called "Hastert Rule" of only bringing bills to the floor that had the strong support of his own party members. But occasionally, he fell back on Democratic votes for spending bills that he regarded as "must pass" despite resistance in his own ranks. A new group had formed to the right of the leadership, calling itself the House Freedom Caucus. Although informal, it could deny Boehner enough votes to neutralize his majority. Facing a potential effort to remove him as speaker, Boehner abruptly resigned in October 2015. He had been speaker for less than five years.

Rather than promoting the next man on the leadership ladder, in that moment the House Republicans turned instead to Ways and Means Committee Chairman Paul Ryan. A member of the Class of 1998, Ryan had been chairman of the Budget Committee and regarded as a master of the most vexing tax-and-spend issues. He had also been the party's nominee for vice president in 2012.

But Ryan was reluctant. He liked his job at Ways and Means. He hoped a Republican in the White House after 2016 would empower his longtime agenda of tax cuts and spending cuts and reforms to "entitlement programs" — even Social Security and Medicare.

As it turned out, Ryan got a Republican president in Donald Trump who would push for tax cuts and sign the bill. But the rest of the Ryan program seemed further from enactment than ever. And Ryan's own relationship with the president had never entirely recovered from the day in October 2016 when Ryan withdrew his invitation for candidate Trump to join him at a rally.

Given all these considerations, it becomes easier to understand why a relatively young man would leave such an important job — seemingly at the top of his game.

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