They don't dress like that in the White House anymore. Joseph Keppler/

Dressing for success apparently has taken on a whole new meaning for politicians. History Professor Deirdre Clemente of the University of Nevada, Las Vegas, says rather than adopting the formal dress of the past, presidents are trying to appear as regular guys to make the connection with voters.

Clemente, author of “Dress Casual: How College Students Redefined American Style,” says the move toward “casualization” started when President Harry S. Truman appeared in a Hawaiian shirt on the cover of Life magazine in 1951 as his term in office was winding down. Truman had 62 such shirts.

It’s been downhill from there.

Then came John F. Kennedy. He ditched the hat in contrast to Calvin Coolidge who, it is said, wore a chapeau even while shaving.

Jimmy Carter ushered in the era of dad jeans and cardigan sweaters. Ronald Reagan upped the ante by adding a cowboy hat and denim shirt while George W. Bush added a gigantic belt buckle.

Barack Obama not only wears dad jeans, he often is pictured in his office with rolled up shirt sleeves. Clemente says the meaning of the rolled up sleeves is: “I’m willing to shake off formality and dig in to do the work.”

Critics, of course, have seized on the sleeves, calling it undignified. But fashion gurus disagree. Magazines like Men’s Health and Esquire have offered tips on how to roll up sleeves neatly.

On Election Day, Clemente notes, many Americans likely will vote while wearing yoga pants, T-shirts and sneakers.

What about this year’s presidential candidates?

Democrat Hillary Clinton has made the pants suit her uniform on the campaign trail. Can the house dress be far behind?

Republican Donald Trump wears a baseball cap emblazoned with his campaign slogan at many of his events. Might he ditch his signature hairdo once in the Oval Office?

Racked ranked the personal style of the first 43 presidents, dubbing Benjamin Harrison as the worst, largely for his handshake and teetotaling ways. He also handed the country over to big business.

Richard Nixon, ranked as the 41st worst stylistically, left as his most lasting fashion legacy the Halloween mask of his face.

Who was tops on Racked’s list? Chester Arthur, described as a “flashy Manhattan dandy, always ready with a joke or a bribe.” He reportedly had 80 pairs of pants.

The White House, however, has a dress code, albeit eased in the Obama years. Since he cranks up the heat, it’s OK not to wear a jacket and tie in the Oval Office; the dress on weekends is business casual.