Cowboy fashion is critical during the Calgary Stampede when even the most staid bankers, sales clerks or high-ranking oil executives trade in their usual attire for cowboy hats, boots and jeans.

Those who don't at least make an honest effort to "go cowboy" may find themselves the target of ridicule from co-workers or even people on the street.

There's no exemption for politicians who want to show that they're down with all that western stuff as they rub elbows with the locals and try to rustle up some votes.

But a warning to politicians who aren't adept at corralling their "inner cowboy."

No one has forgotten the picture of Stephen Harper wearing a too-tight leather vest and a shapeless hat reminiscent of a 1940s comic cowboy sidekick. Ditto for former prime minister Jean Chretien who tucked his jeans into his cowboy boots in a western fashion disaster.

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In 2005 Stephen Harper's black, leather vest received bad reviews. (Jeff McIntosh/Canadian Press)

Elizabeth May of the Green party learned her lesson the hard way when she was skewered for her clothing choices during her first foray to the Stampede as leader.

"The first time I came I thought, OK, I'll go and get denim things at a second-hand chain in Nova Scotia, because I didn't have a lot of money to spend. I thought, 'This will do OK' and I was lambasted and so now I've learned," she said with a laugh.

"Come to Calgary a day early and get outfitted ... Don't mess around thinking you can do it yourself."

The political tenderfoot at this year's Stampede took that advice to heart.

Novice federal NDP boss Tom Mulcair tweeted before his visit that he was heading to a western-wear store in Calgary to get outfitted — and it paid off.

Brian Guichon, owner of Riley & McCormick Western Stores, who  plays the Stampede's Mr. Blackwell, says he was a bit surprised, but decided Mulcair was the best-dressed politician this year.

"Thomas has got the nice jeans. Notice how the jeans are stacked at the bottom. That's so when he gets in the saddle it still covers the boot," Guichon said.

"He seems to have nailed it with a good western outfit and he looks like he belongs, looks like he's stepping into the role," he said of Mulcair's blue-and white plaid western shirt, white hat, jeans and shiny black cowboy boots.

"Also, he's got a good belt buckle and good comfortable jeans. The hat looks a little on the small side, but it sure suits him well."

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Prime Minister Stephen Harper looked more comfortable in western-wear this year, according to fashion critics. (Jeff McIntosh/Canadian Press)

Guichon also had high praise for Harper's matching black cowboy hat and boots, blue jeans and a checked shirt.

"He's done well. He's looking more and more comfortable in his western wear and he's coming along."

Guichon rated the prime minister as second-best with Calgary Mayor Naheed Nenshi at No. 3 with the sleeves of his cowboy shirt casually rolled up.

"He looks like the mayor of Cowtown." 

May, who went from last in the fashion ranks to first a number of years ago, held her own this year.

"Elizabeth has a nice plaid shirt on. She's got a nice silver belt buckle and the hat looks like it fits and she wears that well. Elizabeth has really cowgirled up."

But added he wasn't "real sure on rolling up the jeans. That's a little bit of a faux pas."

Alberta Premier Alison Redford also got high marks, especially for her "blingy" belt, western skirt and cowboy boots that looked like they had actually seen a horse.

Liberal MP Justin Trudeau was given credit for his hat, belt buckle and cowboy boots, but there was a problem with the overall look.

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Liberals Justin Trudeau and Bob Rae were accused of looking bland and less authentic in their themed-clothing. (Jeff McIntosh/Canadian Press)

"I'm not sure if that's a western shirt ... or just a dress shirt that's been rolled up at the sleeve. It's a bit blase. He could have done better if he had something with a little more western flair."

The biggest disappointment was Liberal Leader Bob Rae.

"Sorry Bob. It looks like Harry Rosen's denim shirt down from Toronto and it's hard to say even if that's a western buckle and belt," Guichon said.

"The shoes don't cut it. A pair of boots would probably suit him up a little better. He doesn't look all that comfortable ... it's a little half-hearted.  

"If I were to say who would be the worst — I think Bob Rae would be at the bottom of the poll. Bob's got some work to do."

Guichon summed up what all politicians should keep in mind if they plan to visit the Greatest Outdoor Show on Earth.

"Everybody takes it as a given that when you're around here ... you dress western.

"You don't show up in a tie and jacket to a western barbecue."