Sen. Robert Byrd (D-W.Va.) did much to shore up his position as chairman of the Appropriations Committee on Wednesday.

After a week of whispered speculation about whether the 90-year-old senator was still up to the job or had become too frail and unfocused after a fall and bout of illness, Byrd returned to the public eye with a degree of aplomb.

He arrived at a hearing on President Bush’s $108 billion request for war funding in a wheelchair, but nevertheless looked businesslike and sounded blunt and breezy.

At the end of the two-hour hearing, during which he and other panel members grilled the president’s budget director, former Rep. Jim Nussle (R-Iowa), Byrd commented that it was time for his critics to “shut up.” It is likely that they will do so for a short while, but not indefinitely.

As head of perhaps the most important committee in the Senate, Byrd inevitably has people eyeing his chair enviously. The Hill reported last week that Sen. Patrick Leahy (D-Vt.) has expressed an interest in taking over. There is nothing wrong with this.

And although Senate occupants suggest that the institution is a dignified and morally admirable place, it is actually prone to as much ambition and disingenuous intrigue as any other corpus of politicians.

Politicians enjoy treading water or sliding backward no more and probably less than the average person. They constantly try to climb what Benjamin Disraeli recognized as a “greasy pole.” Thus every chairman is wise to look over his shoulder.

In addition, it is perfectly legitimate for Capitol Hill’s denizens to wonder whether a man who has reached such a great age as Byrd is still capable of running his major committee through the slog of appropriations season.

Retirement in all other walks of life usually comes many years, sometimes decades, before the retiree reaches Byrd’s venerable years. Byrd may indeed be fully capable and, with his wealth of experience, still the best person to run the spending panel. But it would be odd to suggest that the issue should not be raised.

Past members of Congress have died in office, and sometimes it is subsequently admitted that their capacities were sorely diminished and their retirements long overdue. Respect, deference and a reluctance to strike at a man who has become a Capitol Hill institution all have their place, but they do not displace the litmus test of competence.

Tellingly, Byrd and everyone watching him knew on Wednesday that he needed to display a brisk confidence to help him buttress his assurances to Senate Majority Leader Harry Reid (D-Nev.) that he is feeling strong and recovering well. At least for now, he seems to have done what was necessary.