When the Judiciary Committee reconvenes to determine the fate of Supreme Court nominee Brett M. Kavanaugh, four veterans will sit in the middle of the panel dais with a combined 150 years of Senate service.

Supporters will see an up-by-his-boostraps farmer, a trailblazing feminist, a prolific conservative legislator and a liberal legend. Critics will see two Republicans and two Democrats in the twilight of their careers leading one of the most sensitive and consequential hearings in 30 years.

No one will see a future president. No one.

And yet all four senators have a potential claim on presidential succession.

A random quirk in Senate custom grants the position of president pro tempore to the longest-serving member of the majority party. While largely honorific, that post falls behind the vice president and House speaker in the line to the nation’s highest office.

Sen. Orrin G. Hatch, 84, is the Senate’s pro tempore, but the Utah Republican is retiring at the end of the year. Depending on who wins the majority, either Sens. Charles E. Grassley, 85, or Patrick J. Leahy, 78, would take the position. The Iowa Republican and Vermont Democrat each won a full six-year term in 2016.

Just behind Leahy, if something would force him from office, is Sen. Dianne Feinstein (D-Calif.), the 85-year-old who is running for reelection in November.

Congressional historians believe this should be fixed.

“It doesn’t make a whole lot of sense to have the office of the presidency devolve on an octogenarian,” said Ross K. Baker, a distinguished professor at Rutgers University who did five fellowships in Senate offices the past two decades.

To be sure, Baker himself turned 80 in June. He believes that the pro tempore position should just be given to the majority leader.

“It makes a great deal of sense,” he said.

That rules change would hand the post to Senate Majority Leader Mitch McConnell (R-Ky.), who at 76 is two years younger than Leahy.

At least that leadership position comes through an election process in the party caucus. Recent majority leaders have included Thomas A. Daschle (D-S.D.), 53 when he took the job, and Bill Frist (R-Tenn.), then 50.

The custom of granting the longest-tenured senator in the majority the pro tempore position begin in the late 19th century, according to a 2015 report from the Congressional Research Service. For most of the 19th century — when the Senate operated without majority and minority leaders — the Senate elected the pro tempore position much like today’s leadership elections.

The quartet of senior senators will face a more intense spotlight if a Judiciary Committee hearing is held with Kavanaugh and Christine Blasey Ford, the woman who has accused the judge of sexual assault when they were teenagers.

The four senators get their collective ire up against “ageism” when someone suggests they are too old to run a committee hearing, but it’s an open secret on Capitol Hill that they have slipped a bit.

Grassley, the Judiciary Committee chairman, often tells reporters and staff to hold off on conversations during subway rides in the Capitol because it is too hard for him to hear. During the last two years, Hatch has made many statements on taxes and health-care legislation that aides were forced to clarify later. Leahy is showing his age, walking with a distinctive stoop.

And Feinstein, the top Judiciary Democrat, has struggled at times with details. Late last month, approached by reporters from The Washington Post and legal news site Law 360, Feinstein could not remember questions she posed to Kavanaugh in her meeting earlier that afternoon.

“Well right now I can’t think of them, but all I can say is, we had a good meeting,” she said. “I very much appreciate the conversation. If I had known I was going to be asked, I would’ve written it all down.”

Grassley grew up on a family farm, where he still works. He boasts about running three miles four times a week. Leahy celebrates each birthday by scuba diving to the depth of his age.

As she runs for reelection, Feinstein highlights her experience. “I think people understand I’m now ranking on Judiciary, going into one of the biggest moments that this party has,” she told reporters in July at her state’s Democratic convention.

Leahy believes veteran senators are on the march. As the top Democrat on the Appropriations Committee, he worked closely with the 84-year-old chairman, Sen. Richard C. Shelby (R-Ala.), during a very productive run this summer.

“Senator Leahy is as effective as a legislator today as he’s ever been,” said David Carle, Leahy’s spokesman.

And Hatch, the outgoing Senate pro tempore, defended all four.

“No one in American government matches these four senators in terms of demonstrated leadership, accrued wisdom, and institutional memory — in other words, the very qualities we’d need in a president in a moment of national crisis,” Matt Whitlock, his spokesman, said in a statement.

Institutional memory is a crucial trait, but President Grassley? Or President Leahy?

The 2001 terrorists attacks are believed to have initially targeted the White House and the Capitol, and on that day the sitting Senate president pro tempore, Sen. Robert C. Byrd (D-W.Va.), wandered outside the Capitol’s East Front amid the chaos with no staff.

Ever since, the post has come with a security detail and a car, as well prime office space in the Capitol and a handful of paid staff.

Also, with President Trump’s 2016 campaign under investigation, it’s not completely implausible to see the vice presidency vacated, with Mike Pence taking the top job. In such a scenario, a Democratic-controlled House might not quickly confirm the new vice president.

During such an extended period, the line of succession next year could rest with a House speaker who is now 78, Rep. Nancy Pelosi (D-Calif.), and 85-year-old Grassley.

The reality is, no one wants to go to these venerated lawmakers and take away the perks of the pro tempore office, offending them.

Yet the easy answer comes from history: In 1977, after former vice president Hubert Humphrey (D-Minn.) returned to the Senate, the chamber created the temporary post of deputy president pro tempore.

Such a rules change could easily be made now. It would allow the most senior senators to continue holding an honored position while taking them out of the line of succession.