A Colorado store owner is closing his doors after a decision to pull all Nike items in protest of the company’s use of Colin Kaepernick in an ad campaign hurt sales. (AP)

Owning a small business is tough. So tough, a high percentage of them fail within months of opening.

So if you’ve kept a business going for more than 20 years, you’re probably doing something right.

Until you don’t.

A sports store without Nike?

Prime Time Sports, a sporting goods store in Colorado Springs, Colo., is closing its doors after more than 20 years in business. On Monday, owner Stephen Martin and employees posted signs in the store saying everything was 40 percent off, the beginning of the clearance sale.

Last year, Martin decided to pull all Nike items from his store, which sells all manner of items with sports team logos — apparel, mugs, blankets, wall plaques — after Nike’s ad campaign featuring Colin Kaepernick.

Nike is the official manufacturer of all NFL player jerseys, and much of the affiliated merchandise, like team hats, jackets and hoodies.

Martin held a clearance sale last year for all Nike items in his stock.

‘Like a gas station without gas’

Martin “just can’t keep the doors open anymore” since his decision, because sales have declined and he can no longer afford the lease on the store.

A sports store that doesn’t sell Nike — it’s kind of like … well, Martin might say it best.

“Being a sports store without Nike is kind of like being a milk store without milk or a gas station without gas,” he said.

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Indeed it is. Indeed it is.

‘Perhaps there are more Kaepernick supporters than I realized’

Martin has a big problem with players who protest during the anthem, canceling a planned autograph session with Denver Broncos linebacker Brandon Marshall in 2016 after Marshall kneeled, protesting Marshall’s decision to use his platform to bring attention to issues of racial injustice.

“As much as I hate to admit this, perhaps there are more Brandon Marshall and Colin Kaepernick supporters out there than I realized,” Martin said.

Looks like it.