Sen. Daniel Inouye, D-Hawaii,, who passed away on Monday, was many things - a war hero, a civil rights pioneer, an old bull of the Senate, a tireless fighter for Hawaii, a committee chairman, and both last and least, he was president pro tempore of the United States Senate. It's a title that sounds impressive - it has both "president" and Latin in it - but in fact it's meaningless.

The pro tempore designation is just an honorific routinely bestowed on the most senior member of the majority caucus. Before Inouye, it was Robert Byrd's gig. Before him came Ted Stevens. Before that it bounced back and forth between Byrd and Strom Thurmond. Nobody really needs to care about this as anything other than a trivia question answer except that a thoughtless provision of the Presidential Succession Act of 1947 puts its holder in line for the presidency.

And not just some random place in line. Close to the front.

Imagine some disastrous scenario - a terrorist attack most likely - that simultaneously kills or disables the president, vice president and House speaker all at once while they're negotiating the latest budget crisis. Who's next in line? The president pro tempore of the United States Senate, someone nobody intended to put in any kind of position of national leadership. Indeed, it is almost invariably someone his colleagues have passed over as caucus leader in favor of a senator who is younger and more reflective of the current spirit of politics.

The president pro tempore is in the order of succession thanks to the kind of logic that makes a lot of sense in the halls of Congress and no sense outside of it. The speaker of the House got on the list, so the dignity of the Senate demands that they get someone in there, too. And if not the president pro tempore, then who?

In real-world terms, of course, the Senate equivalent of the House speaker is the majority leader. But in technical terms, that's not correct. Speaker of the House of Representatives is an official federal government title. Though in practice the speaker is simply the leader of the majority party in the House, in theory he or she is the speaker of the whole House.

The majority leader of the Senate, by contrast, merely holds a position in his party's caucus. The senator who holds a national office is the president pro tempore of the Senate. At the same time, the Senate is by its nature a tradition-bound and seniority-driven institution, so it sticks with the convention that the office must always be given to the most senior member of the majority party rather than to someone who anyone thinks would be a good leader of the country.

The problems with this setup begin with the problems it has in common with putting the speaker in the line of succession. Most problematically, an assassin could effect a change in partisan control of the executive branch - exactly what the country doesn't need in a time of crisis.

The Senate compounds these problems with the fact that the most senior senator is often quite old. Inouye's death is a sad event, but hardly shocking. He'd been using a wheelchair all year and was dependent for months on an oxygen concentrator to maintain breathing even before his most recent turn for the worse.

Inouye's predecessor, West Virginia's Byrd, also died in office and for the last 18 months of his life, the extent of his deteriorating health condition was a closely held secret of his inner circle. Strom Thurmond of South Carolina served as president pro tempore even after voluntarily relinquishing the right to chair a committee out of recognition of his advanced age and declining capacity for work.

With Inouye dead, the honor passes to Pat Leahy of Vermont, who's unusually young for the office at the age of 72 and with no known infirmities beyond longstanding blindness in one eye. His counterpart on the GOP side, Orrin Hatch, is 78 and was just elected to a fresh six-year term.

That said, the whole purpose of having a Presidential Succession Act in the first place is to ensure that some sensible contingencies are put in place. And turning the White House over to an elderly senator of the majority party is not sensible. And unlike many national problems, this one could be easily fixed.

Having the presidency pass directly from the vice president to the secretary of state and then down through the ranks of the cabinet officers is logical, simple and does nothing to advantage or disadvantage either party or its vision in the long term.

As chairman of the Judiciary Committee, Leahy himself has the relevant jurisdiction and could do the country a huge favor by stepping up and authoring a bill to selflessly remove himself from the order of succession. Ninety-nine years out of 100 it won't make any difference, but some day it just might, and we'll thank him.

Matthew Yglesias is Slate's business and economics correspondent.