Washington ? Despite all the hyperventilating about whom they’re likely to be, vice presidential candidates rarely make much of a difference in the fall elections.

“They can only make a small difference at the margins,” said James Riddlesperger, an associate professor of political science at Texas Christian University, in Fort Worth.

They don’t get much news coverage after an initial burst when they’re selected, and they often lose their own states.

Yet every four years – especially this one, when two people are about to be rocketed into the spotlight – a frenzy of speculation builds about whom it’s going to be.

There are reasons for that:

¢ The choice is the presumptive nominee’s first big presidentlike decision, so it reveals something about the nominee.

¢ There are potential intangible electoral advantages.

¢ And it’s summer, when speculating about presidential ticket mates becomes a national pastime.

Making a difference

Only twice in recent history, however, did a No. 2 pick arguably make an obvious difference, in 1960 and 1976.

Democrat Lyndon Johnson, then a Texas senator, “probably delivered the state for (John) Kennedy,” Riddlesperger said. Kennedy won the state’s 24 electoral votes in 1960 with 50.5 percent of the popular vote.

In 1976, Democrat Walter Mondale, then a veteran U.S. senator, was invaluable to little-known presidential nominee Jimmy Carter, said Joel Goldstein, a vice presidential expert at St. Louis University.

Mondale’s opposite number was Republican Sen. Bob Dole of Kansas, who had a reputation as a slashing critic of his opponents. He burnished that image during his debate with Mondale by railing against “Democrat wars.”

The calmer Mondale looked like a statesman, Goldstein recalled, and was dispatched in the campaign’s final days to swing states such as Ohio, which the Democrats won by 0.2 percentage point.

“It was as though he was running for an Ohio Senate seat,” Goldstein chuckled.

Those elections were the exceptions.

Challenging choices

A few controversial modern picks, notably Richard Nixon in 1952, Spiro Agnew in 1968 and Dan Quayle in 1988, wound up on winning Republican tickets.

Nixon saved his place on the 1952 ticket with his emotional “Checkers” speech – invoking his dog to gain sympathy amid an alleged scandal – six weeks before the election. Dwight Eisenhower carried 39 of the 48 states with Nixon aboard.

In 1968, Agnew, then in his second year as the governor of Maryland, was best known for his blunt talk, but presidential nominee Nixon won 32 states and the election with Agnew in tow.

Those examples proved the rule, analysts said, that people vote for presidents, not their running mates.

“We can’t find any evidence in our recent polling that the vice president made a significant difference,” said Frank Newport, the editor in chief of the Gallup Poll.

Still, the veep pick can mean something. Political strategists weigh whether a given candidate could help swing a much-needed state in a close election.

That’s why there’s talk about whether former Massachusetts Gov. Mitt Romney could help Republicans win Michigan – Romney’s father was the governor there in the 1960s – or whether former Democratic Sen. Sam Nunn could help Democrat Barack Obama carry Nunn’s home state of Georgia.

Closely watched decision

More important, the pick offers clues about how prospective presidents make personnel decisions.

“The choice can shape how a presidential nominee is perceived,” Goldstein said.

In 1992, Bill Clinton was still introducing himself to a skeptical American public, and his choice of Al Gore “brought value to the ticket,” recalled Sen. Ben Nelson, D-Neb., because it reinforced the idea that Democrats had a young, forward-looking team.

Eight years later, George W. Bush’s choice of Dick Cheney “signaled what kind of a chief executive officer he was going to be,” said Allan Louden, an associate professor of communication at Wake Forest University, in Winston-Salem, N.C., by picking someone with an impressive Washington and business resume.

Chances are, though, that the vice presidential picks will have no discernible effect on the outcome, so long as the presidential nominees follow a key rule of ticket-making: First, do no harm.

“The choices may not make a difference,” Goldstein said, “if they both pick somebody good.”