Democratic presidential candidate former tech executive Andrew Yang speaks during the second night of the first Democratic presidential debate on June 27, 2019 in Miami, Florida.

Raising money for presidential campaigns is serious business, but that doesn't mean candidates can't have a little fun with it.

Campaign sites this cycle are full of routine merchandise such as hats and t-shirts, but they're also featuring some oddball items that voters might not necessarily associate with hard-hitting presidential politics.

For instance, Washington Gov. Jay Inslee is promoting an illustrated children's book about snow melting. Other candidates — Sen. Kamala Harris, entrepreneur Andrew Yang and President Donald Trump — are offering summer-themed goods like "Koozies," which keep drinks cold.

There are even more eccentric products. Yang supporters can purchase a "no tie summer look" for $40 that comes with a certificate. The campaign introduced the "item" after pundits and late-night comedians criticized the entrepreneur for showing up to the first Democratic debate without a tie.

Yang also has an entire collection devoted to summer, but Trump wins when it comes to which candidate has the most items centered around the season. Trump's campaign website features MAGA swimsuits for men and women, $65 beach towels and sunglasses holders, among other seasonal items.

The practice of selling campaign merchandise might go back to the mid-nineteenth century, when candidates provided free alcohol at campaign rallies, said Eric Gander, associate professor of public argument at Baruch College. But selling campaign merch has also always been a way for candidates to maintain control of their image, he said.

"In America, we give maximum latitude to our citizens to talk about politicians, even if those citizens form companies that sell products that make money off likenesses of those politicians," Gander said. "So, why wouldn't the candidate himself or herself want to get in on the action? There's a lot of money to be made in merchandizing. It's also great advertising for the candidate."

Some candidates are putting an extremely personal touch on their campaign merch. Available at South Bend Mayor Pete Buttigieg's campaign store is a "Chasten for First Gentleman" t-shirt and another with his and husband Chasten's names, along with Truman and Buddy, the names of their two dogs.

Other candidates have items that mock Trump. Former Housing and Urban Development Secretary Julian Castro's campaign page, called Adiós Trump, offers Koozies, baby onesies, t-shirts, caps, buttons and stickers, each conspicuously brandishing the words of farewell directed at the current president. Former Rep. John Delaney's anti-Trump gear includes $10 playing cards with a caricature of Trump's face on the joker card.

Sen. Cory Booker has a line of stickers out that pokes fun at 2020 rival and former Vice President Joe Biden. The stickers feature Booker's face and the words "future president," which Biden mistakenly used during the second democratic debate in reference to Booker.

Other noteworthy items include:

From Delaney: stress grips and golf balls

A Bernie Buck advertising the 99% and selling for $27

10 pamphlets about Bernie's campaign in Spanish (also available in English), selling for $6

Packs of three stickers for $10 from Warren

A Trump-approved presidential medal

Sen. Kamala Harris, former Colorado Gov. John Hickenlooper, and Sen. Kirsten Gillibrand have mostly conventional items for sale, like t-shirts, caps, and totes.

New York City Mayor Bill de Blasio doesn't have a store up yet, but a campaign spokesperson said it's in development.