One of the worst traditions of the U.S. Senate has been in place for 80 years: the selection of the longest-serving senator from the majority party as the largely ceremonial president pro tempore of the Senate.

But the position carries one huge responsibility.

The Presidential Succession Act of 1947 dictates who would become acting president if the president and vice president were suddenly out of the picture, a concern that arose with the dawn of the atomic age. Under its terms, if both leaders were suddenly dead, the speaker of the U.S. House would be next in line for the nation’s top job. If the speaker can’t do it, the post falls to the Senate’s president pro tempore.

Today, that would be U.S. Sen. Charles Grassley of Iowa, a 91-year-old Republican who has been a senator longer than Vice President JD Vance has been alive.

He views his accession to the White House as unlikely.

“If something happened to the president, the vice president and the speaker of the House, it’d almost have to happen at the same time for me to kick in,” Grassley told Iowa Radio. “I always say: ‘Well, who would want to be president under those circumstances?’”

Since Grassley isn’t up for reelection until 2028, he could hold the post until he’s 95 if Democrats fail to recapture the Senate in 2026.

Interestingly for Mainers, if the GOP retains its majority, his most likely successor is 72-year-old U.S. Sen. Susan Collins, though she would have to win reelection in 2026.

Grassley and U.S. Sen. Mitch McConnell of Kentucky are the only Republicans with more seniority than Collins. McConnell has already said he won’t seek another term in 2026. That means Collins could be the third in line for the White House should something happen in the final weeks of Donald Trump’s presidency in January 2029 and perhaps beyond.

Whatever her faults, Collins is reasonably healthy and sharp. Nobody would say the same about either Grassley or McConnell. Both are past their prime. Yet some of the presidents pro tempore in my lifetime were in far worse shape than either of them.

When U.S. Sen. Strom Thurmond of South Carolina held the position in his dotage, his colleagues recognized that he wasn’t fit to serve so they created an even more ceremonial office for him: president pro tempore emeritus. It is now awarded to any senator who previously held the non-emeritus version of the position, including U.S. Sen. Patty Murray, a Washington Democrat.

In the country’s first century, the president pro tempore, a post called for in the Constitution, was second in the line of succession, after the vice president. The House speaker at the time seemed too inconsequential for so weighty a responsibility.

Then from 1886 until 1947, neither the Senate president nor the House speaker was eligible at all. During that period, the only Mainer who held the job, Republican William Frye of Lewiston, hung onto the role for more than 15 years, from 1896 until his death in 1911.

Frye was a pretty good choice, but most of his successors have been politicians who are no longer at their best. Many of them are also largely unknown beyond their own states.

It doesn’t have to be like this. Senators could face the potentially awesome consequences of the line of succession act and choose someone other than their oldest brethren. After a calamity that took out the nation’s top leaders, the United States would need someone at the helm who could be trusted to serve effectively, with dignity and honor.

Unless they want to change the legislation detailing the line of succession to take Congress off the list again, senators ought to pick somebody for the title who they think has the stature and skill to handle service in the Oval Office.

Mainers will likely decide in 2026 if they think Collins is ready for another six years representing the Pine Tree State in the Senate. Unwittingly, they might even be electing the next president of the whole country at the same time.