Washington (CNN) The white Obama "O" logo pops on the black sneaker. Below, written in all caps is "MBK Alliance," for the former president's My Brother's Keeper initiative. And on the midsole, the "SC" logo for Steph Curry's shoe line. It's an all-star collaboration between one of the biggest brands in politics and one of the biggest brand in signature sneakers, a one-of-one, worn by Curry once, at Washington's Capital One Arena in February. Curry put them up for a charity campaign this week, with fans able to donate $10 for a chance to win them.

The night Curry wore his custom Obama Curry 4s, the Golden State Warriors beat the Wizards 109-101. Earlier in their visit to D.C., the Warriors had bucked the traditional White House visit made by defending NBA champs, visiting the Smithsonian National Museum of African American History and Culture with a group of students instead. Curry had said months earlier that he didn't want to go. He said so, in fact, the same day President Trump, while speaking at a campaign rally in Huntsville, Alabama, used the term "son of a bitch" to refer to athletes who knelt during the National Anthem and said athletes should be fired for kneeling. The following day, about 20 minutes after Fox News aired a segment on Curry's comments, Trump responded to it, tweeting that Curry's invite was rescinded.

So Curry's shoes felt like an exclamation mark on the trip. They were a show of support for the previous president and his work, but also a show of contempt the current one, and in the heart of his adopted presidential hometown no less. And they were part of an emerging trend.

As politics has collided with professional sports during Trump's time in office, athletes have turned to fashion to send a message. Cleats and sneakers have become a canvas of political and social expression for some of today's biggest and most outspoken sports stars -- and a way to make a statement while standing.

Wide receiver DeSean Jackson #11 of the Washington Redskins wears cleats displaying police caution tape prior to a game against the Cleveland Browns at FedExField on October 2, 2016 in Landover, Maryland.

Customized causes

Marcus Rivero -- who goes by @solesbysir on Instagram -- paints shoes for athletes. He started doing them for members of the NFL's Miami Dolphins, and by now he's made custom-painted shoes for at least one player on every team in the NFL, as well as for athletes in the NBA and MLB, soccer players overseas, and boxers.

"When I first started doing this custom painting stuff, it was just changes blue to yellow, changes purple to black, and then it started becoming more messages," he told CNN's COVER/LINE. "Then they started to get deeper meanings."

In 2014, the Washington Redskins' DeSean Jackson, a longtime client for Rivero, had a specific request. He wanted "something cool" on his cleat, Rivero recalled him saying, but he wanted something else too. A New York grand jury had just decided to not indict a police officer in the death of Eric Garner and Jackson wanted his cleats to read "I can't breathe," the words Garner could be heard struggling to say in a video as the officer held him in a chokehold.

"It was my first political shoe," Rivero said. "I really wasn't trying to take a stand for anything, my stuff was just artwork, and when he told me that, I said, 'OK, I'll come up with something.'"

The result was a snakeskin pattern in Washington's colors, burgundy and gold, with the words written across the front, fading out at the end.

"That went pretty viral pretty fast," Rivero said.

While most of the shoes he paints are apolitical, he's begun to receive more requests for paint jobs related to news events. Following the 2016 Dallas shooting, he painted another pair for Jackson, this time, sky blue covered in bright yellow caution tape, as a statement against violence. After the Las Vegas shooting in October, the Washington Nationals' Bryce Harper wore "Pray for Las Vegas" cleats with various images from the Strip.

For week 13 of the most recent NFL season, the league encouraged players to support charities through its My Cause, My Cleats initiative. It's Rivero's biggest week of the year, and he starts working on cleats far in advance to fulfill all his client's requests. Tennessee Titans' Rishard Matthews selected Know Your Rights, the charity of his college friend Colin Kaepernick, and Rivero painted Kaepernick's name and an image of him kneeling with his hair styled into a fist.

"That one probably got the most political attention, and it was very controversial," Rivero said. Matthews didn't end up playing that week, due a hamstring injury. Still, "the shoe had made its mark even before the game started," he said.

🏀👟🏈 A post shared by COVER/LINE (@cnncoverline) on Apr 13, 2018 at 8:32pm PDT

An advocating addition to a uniform

Athletes are restricted in what they can wear on the court or field. But their shoes can be an exception.

"The only way that most guys in the league can get away with expressing themselves is their footwear," said Rachel Johnson, a stylist who's worked with some of the NBA's biggest stars, including LeBron James, Chris Paul and Amar'e Stoudemire. Sneakers, she said, are, "the smartest and most innovative way that they can express themselves without getting fined."

While the NFL has traditionally had strict guidelines about cleats, down to the color of the laces, rules have loosened. In 2016, a half dozen players wore red, white, and blue cleats for the 15th anniversary of 9/11, and none of them were fined, and last year, personalized cleats were allowed for pre-game. The NBA has also relaxed its shoe rules. While the league once required players to match their teammates, athletes are now allowed to mix and match from their team's color palette and wear special colors for events and holidays. It's allowed athletes greater expression, and opened the way for shoes with political or social messages.

Curry's first Obama sneaker came just days into Trump's time in office, on MLK Day 2017. It was a Curry 3 with a presidential seal on the tongue, Obama's signature on the sole, along with the phrase "Back2Back" a reference to Curry's back-to-back MVP titles and Obama's back-to-back electoral college victories.

Shoes with the American flag or to honor service members are popular. Baseball's Harper wore a fatigue brown "Honor The Fallen" version of his Harper 2 on Memorial Day. Michael Bennett -- the son of a veteran who was then with the Seattle Seahawks and now with the Philadelphia Eagles -- was one of the NFL season's earliest anthem protesters and wore cleats with the image of a kneeling soldier for POW/MIA. His Seahawks teammate Blair Walsh supported The Bully Project with cleats covered in the words "Speak Out," while the San Diego Chargers' Kellen Clemens wore cleats for National Right to Life.

The Miami Heat's Dwyane Wade turned his sneakers into a tribute to Joaquin Oliver, a Wade superfan and Marjory Stoneman Douglas High School student killed in the shooting. Wade wrote Oliver's name on his shoes and gifted Oliver's family a pair of his Way of Wade brand sneakers customized with Douglas High's eagle mascot.

The sneakers of LeBron James #23 of the Cleveland Cavaliers during the game against the Boston Celtics on October 17, 2017 at Quicken Loans Arena in Cleveland, Ohio.

The statement LeBron James made with his sneakers was "Equality," written in gold all-caps across the back of his LeBron 15s.

James debuted the 15 during New York Fashion Week in September 2017 at a show for the brand Kith. The 15 was sleeker and sexier than some of his most recent sneakers. Previous editions of the line were bulky and muscular, built like a superhero, but the 15 was built for someone who has a runway show at 7 and a basketball game at 8. The day of the Cavaliers opening game, James appeared in photos for a GQ cover story wearing a gold pair of his sneakers along with $845 Dolce & Gabbana pants and a $3,395 Alexander McQueen peacoat with the collar popped. And then that night, they became political symbols.

Cleveland played the Boston Celtics at Quicken Loans Arena, their home court (and previously, the site of the 2016 Republican National Convention where Trump was made his party's nominee). James wore pair of black "Equality" 15s, a continuation of the Nike campaign he helped introduce in 2017. When the Cavs came to Washington, he wore them again, this time one black, one white.

"We're not going to let one person dictate us, us as Americans, how beautiful and how powerful we are as a people," he said after the game, referencing Trump, according to the Washington Post . "Equality is all about understanding our rights, understanding what we stand for and how powerful we are as men and women, black or white or Hispanic. It doesn't matter your race, whatever the case may be, this is a beautiful country, and we're never going to let one person dictate how beautiful and how powerful we are."

The shoes aren't sold in stores, but in early March, Nike held a 400-pair giveaway, 200 in white, 200 in black, with proceeds going to the same African-American history and culture museum visited by the Warriors in February.

Feet do the talking

This NBA season has seen other examples of clothing being used as a vehicle for political speech. The Sacramento Kings and Boston Celtics wore shirts that read "Accountability. We are One" following the killing of Stephon Clark in March. And a special Nike City Edition line of uniforms for the league included jerseys for the Memphis Grizzlies inspired by the Civil Rights-era "I Am a Man" protest sign, while the Phoenix Suns had the latest edition of their "Los Suns" jerseys, used previously following the passage of controversial immigration enforcement legislation in Arizona in 2010.

But shoes offer players a level of individual expression shirts and jerseys do not. And they play a particular role in fashion for the American man.

Shoes -- and sneakers in particular -- are where many American men first began to express themselves. As the suit, the traditional uniform of masculinity, gave way to new ideals like sneakers-wearing sports stars and tech bros beginning in the '80s, it gave men permission to express themselves through their footwear.

"Sneakers were the first way that men could start to take sartorial choices and I think that men continue to take their greatest sartorial choices at the footwear level," said Elizabeth Semmelhack, senior curator at the Bata Shoe Museum and author of "Out of the Box: The Rise of Sneaker Culture." "

The colors that you see in sneakers, the bold designs, oftentimes you don't find those reflected necessarily in other garments that men wear," she said.

Sneakers remain "at the vanguard of male fashion," she added, and because they're associated with athletic masculinity, "they almost don't feel like fashion, which is often feminized, because of these hyper-masculine associations."

And they've proven an effective way to make a statement. While anthem kneeling became partisan and divisive, sneakers and cleats have not yet risen to that level. When Fox News' Laura Ingraham went after James and the Warriors' Kevin Durant, saying they should "shut up and dribble" in February, it wasn't over their shoes, it was over what they said about Trump in an interview. Shoes are more subtle, less in your face. Yet at the same time, they rebel against the call to not speak out as wearable pieces of political pop art.

Johnson, James' stylist, sees political shoes as a sign of athletes maturing. As a generation of players have grown up, they've realized they can use their voice and platform to do more than sell products, and they've become fathers.

"Watching their own children grow up heightens that level of responsibility for them," she said.

Johnson likened the political shoe trend to the sartorial glow-up the NBA has experienced since the mid '00s.

"There was just bad fashion being passed along from season to season and now that there's been this huge fashion evolution, younger players come in and they really understand that they can utilize fashion as a vehicle to express themselves, to express their brand," she said. "I think that that same kind of freedom, and that same kind of courage, that same kind of level of expression is going to be handed down to the young players as they come up, through the political lens."

Johnson said she expects the trend will continue, especially if people tell athletes they can't express their views.

"As long as there are people telling players to shut up and dribble and that they don't have the right to kneel at football games, there's going to continue to be an uprising in the way that players are expressing themselves."

Instagram gallery photo credits: 1. Ned Dishman/NBAE via Getty Images 2. Patrick Smith/Getty Images 3. Patrick Smith/Getty Images 4. Brendan Smialowski/AFP/Getty Images 5. G Fiume/Getty Images 6. Alessandra Mondolfi 7. Nike 8. Justin Sullivan/Getty Images 9. Soles by Sir 10. @stephencurry30 11. Patrick Smith/Getty Images 12. Soles by Sir 13. @Manny_Navarro 14. Rod Mar/Seattle Seahawks 15. Ronald Martinez/Getty Images 16. Soles by Sir 17. @bharper3407