WASHINGTON — Four years ago I wrote a history of the American vice presidency, published by Smithsonian Books. It was subtitled “From Irrelevance to Power,” and it traced the office’s progression from non-entity to respectability over the previous 227 years.

The improvement in the vice presidency’s public regard may well have stemmed from the death in 1945 of President Franklin D. Roosevelt, when his little-known and lightly regarded VP, Harry Truman, was thrust into the presidency.

He took office with no knowledge of the development of the atomic bomb that soon ended World War II, demonstrating the critical importance of keeping the presidential stand-in well briefed on the inner workings of the administration he served.

But it was not until 31 years later when another president, Jimmy Carter, brought his No. 2 man, Walter Mondale, physically into the White House as a full partner in governing, with major functions assigned and awareness of all that was going on internally.

Thereafter, except in a few cases, our vice presidents have been well utilized, particularly as seen in one Republican, Dick Cheney, in the George W. Bush administration, and one Democrat, Joe Biden, in the Barack Obama years.

Readers may have differing opinions about each one, but these men were undeniably involved with their presidents in high-level policy decisions and actively engaged in pursuing the objectives of the man in the Oval Office, as well as their own.

A glaring exception was Vice President Dan Quayle, whose frequent verbal gaffes made him a laughingstock and who was underutilized in policy by his boss, President George H.W. Bush.

What was astounding about the selection of Quayle was that Bush certainly must have remembered how only close he came to assuming the highest office by default in 1981, after President Ronald Reagan was shot and narrowly escaped death.

Now comes Vice President Mike Pence, former governor of Indiana and the favorite of President Trump’s counselor and cheerleader Kellyanne Conway. As Pence’s pollster, she advocated him to Trump, who had no idea who Pence was beyond being certifiably conservative.

Pence has been a near-silent prop in many photo-ops in the Oval Office and environs, and when he does speak he offers predictable boilerplate right-wing nostrums devoid of much charisma.

Loyalty to the president is of course desirable and essential, but Pence has been an ever-compliant toady. His two immediate VP predecessors, Cheney and Biden, were loyalists too in the office. But each on occasion established himself as his own man, and felt free to express himself accordingly, sometimes even to the embarrassment of his president.

Vice-presidential nominees seldom are seen as have any positive effect on the outcome of a presidential election. The last one who did was Lyndon Johnson, whose campaigning in the South was seen as a boost there for New England Catholic John F. Kennedy.

The discussion of vice presidents has become particularly relevant amid the growing speculation over the Mueller investigations into Russian meddling and various Trump business matters, which could lead to presidential impeachment and a Pence presidency.

The last two times a president faced impeachment were in 1974, when Richard Nixon resigned to escape it, and in 1998-99, when Bill Clinton was impeached but was acquitted by the Senate. On both occasions, credible vice presidents were in place.

Nixon had earlier lost his first vice president, Spiro Agnew, who was forced to resign after admitting to financial corruption. Nixon then chose the popular House Minority Leader Gerald Ford, who proved to be an acceptable if not dynamic replacement as a short-term president. But he was defeated for a term of his own in 1976.

Clinton’s vice president, Al Gore of Tennessee, was a well-respected environmental expert and senator, but he was never called to the presidency because Clinton was acquitted. When Gore ran for the Oval Office on his own in 2000, he lost to the junior George Bush.

Mike Pence, as a potential inheritor of the presidency, has little political track record on which to base the claim, if it ever comes to that. But there he is, for better or for worse.

Jules Witcover can be contacted at juleswitcover@comcast.net.