Eli Harold, Colin Kaepernick and Eric Reid, then of the San Francisco 49ers, kneel on the sideline during the anthem prior to a football game in 2016. (Thearon W. Henderson/Getty Images)

When Democratic presidential candidate Pete Buttigieg saw professional football players kneeling during the national anthem to protest racial injustice and police brutality, the Afghanistan war veteran said, he saw Americans “exercising a right that I had put my life on the line to defend."

Buttigieg, who has broken into the top tier of Democratic candidates in early polling, appeared Thursday with The Post’s Robert Costa at a Washington Post Live event, the first of a series of public interviews with President Trump’s prospective 2020 challengers.

Asked for his perspective as a Navy veteran about the demonstrations that for a time roiled the NFL, Buttigieg said, “I felt that I was watching Americans exercise a right that I had put my life on the line to defend.

“The point of defending free speech is not that you expect to be perfectly aligned with every speech act that is protected,” he said. “It’s that that’s a fundamental American freedom. It’s a huge part of what makes America, America. And when that same flag was on my shoulder, I didn’t think of the flag as something that itself as an image was sacred; I thought of it as something that was sacred because of what it represented. One of the very things it represented is the freedom of speech, and that’s one of the reasons I served.”

NFL players, led by former San Francisco 49ers quarterback Colin Kaepernick, began kneeling during the pregame national anthem during the 2016 preseason. As the movement gained momentum, it turned into a political lightning rod, especially after Trump took interest. In 2017, Trump called for players who refused to stand for the anthem to be fired, arguing the practice disrespected the military.

Buttigieg, the 37-year-old mayor of South Bend, Ind., has drawn on his military experience to support anthem demonstrations in the past. In 2017, he tweeted, “I was trained to stand & salute. But freedom — including to protest injustice — is the whole point of the anthem, the flag, and the country.”

He also used his service as a Navy Reserve intelligence officer to draw a contrast with Trump on Thursday, accusing him of faking an injury, bone spurs in his heel, to avoid the draft for the war in Vietnam.

“I don’t have a problem standing up to someone who was working on Season 7 of ‘Celebrity Apprentice’ when I was packing my bags for Afghanistan,” Buttigieg said, citing Trump’s past NBC reality television series.

Last summer, another 2020 Democratic aspirant — then-Texas Senate candidate Beto O’Rourke — went viral during a campaign stop when he responded to a question about NFL player protests.

“Non-violently, peacefully, while the eyes of this country are watching these games, they take a knee to bring our attention and our focus to this problem to ensure that we fix it,” O’Rourke said of the players. “That is why they are doing it. And I can think of nothing more American than to peacefully stand up or take a knee for your rights, anytime, anywhere, in any place.”

His opponent, Republican Sen. Ted Cruz, fired back, saying, “When Beto O’Rourke says he can’t think of anything more American — well, I got to tell you, I can.”

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