When Barack Obama and John McCain finally choose their running mates, voters can feel sure that these two people were carefully vetted from every possible angle and, if elected, will play a real role in the next administration.

It was not always so.

Indeed, this pre-convention lull may be a good time to recall that the person who deserves credit for taking the vice presidency more seriously is one of our lesser presidents, Jimmy Carter.

It took two disastrous vice-presidential selections to end the tradition of naming a running mate at the last minute, without much scrutiny.

One was Spiro Agnew, ultimately forced to resign as part of a plea bargain over charges of evading taxes on bribes from Maryland contractors.

Richard Nixon picked the Greek-American at the 1968 Republican National Convention over another ethnic candidate, Italian-American John Volpe of Massachusetts. Nixon liked the first-term Maryland governor’s hard line against racial demonstrators.

A federal probe brought Agnew down in the midst of the Watergate scandal. The government moved quickly, as Nixon faced possible impeachment.

When he picked House Republican leader Gerald Ford to succeed Agnew under the 25th Amendment, Congress gave him far more scrutiny than prior vice presidents had received.

The other disastrous pick was George McGovern’s 1972 choice of Thomas Eagleton. Aside from an aide’s brief question about whether he had skeletons in his closet, Eagleton received no scrutiny.

Two weeks later, Bob Boyd and Clark Hoyt of Knight Newspapers reported that the Missouri senator had been hospitalized for depression and undergone electric shock treatment. Within weeks, he was forced to quit the ticket.

So when Carter neared the 1976 Democratic nomination, he asked a close friend, Atlanta lawyer Charles Kirbo, to organize a discreet process to investigate the financial and personal backgrounds of likely running mates. Carter would personally interview seven candidates, but only the three summoned to his Plains, Ga., home were serious contenders.

The interviews proved revealing.

When Carter and Sen. Walter Mondale faced reporters, the mood was relaxed, even jovial.

By contrast, Carter’s interview with Sen. John Glenn went so poorly that the former Georgia governor cut it short and took the former astronaut on a tour of local landmarks, including his ancestors’ graves. Their news conference showed little rapport; I recall Carter standing stone-faced while Glenn swatted gnats.

Mondale prepared carefully for his meeting with Carter, after Dick Moe, his astute chief of staff, helped persuade him to seek the spot.

Moe’s interesting 2006 account in Minnesota History, reprinted in the latest Presidential Studies Quarterly, notes that both men “had thought a great deal about the potential of the vice presidency. Carter talked at length about how he saw the office as a wasted national asset. He was determined to use his vice presidency in a way no president had done previously.”

And Mondale, his top aide wrote, “made it clear to Carter that he did not want to be considered if it was to be a strictly ceremonial office; he was only interested in a truly substantive role.”

In their four years in office, Vice President Mondale was President Carter’s top adviser.

The pattern they created has survived. Ironically, Mondale conducted the messiest vetting process when he picked Rep. Geraldine Ferraro as his running mate in 1984 without enough scrutiny of her husband’s financial dealings.

The substantive roles of vice presidents have varied; the Bill Clinton-Al Gore pair came closest to the Carter-Mondale duo, while Dick Cheney gained more power the past seven years than any predecessor.

But there has been no repeat of the Agnew or Eagleton disasters. However the Obama and McCain choices play politically, neither selection is likely to prove insufficiently vetted or to lack a real role.