The ugly protest scenes outside Donald Trump’s rallies are doing more damage to the protesters than to Mr. Trump’s political chances, according to analysts who say the violence and anti-American sentiments are backfiring.

Protesters in Albuquerque, New Mexico, last week toted Mexican flags, burned American flags and clashed with police, racking up $50,000 in damage to the neighborhood.

Perhaps even worse for the rioters, they are likely chasing undecided voters toward the side of the man they are protesting.

“When people show up throwing bottles and waving the Mexican flag, you have had a lot of people who may have not been willing to support Trump who see this and say the enemy of my enemy is my friend,” said former Rep. Tom Davis, who ran House Republicans’ campaign committee for two cycles a decade ago. “There is no question these are helping Trump, and Democrats know that.”

The billionaire businessman’s stern calls to tighten border controls, his vow to build a wall between the U.S. and Mexico and his declaration that Mexican society is sending “rapists” and other bad elements to the U.S. have angered Hispanic activists, who view Mr. Trump’s campaign as a tipping point in politics.

Inflammatory: A protester sets a Donald Trump campaign hat on fire during ... more >

Likewise, his call for a ban on Muslim visitors and some of his comments about women leave many voters wary and some of them angry enough to take action beyond the ballot box.

Attempts to disrupt his rallies from the inside have drawn stiff rebukes from the 69-year-old candidate, who has talked about punching protesters and described others as undatable goobers, diaper-wearing morons and fat blowhards.

“Go home to mommy,” he told a protester at rally last week in Albuquerque.

Outside of the Albuquerque rally, things were even worse.

Six city police officers sustained “significant injuries” and another was treated for smoke inhalation from fires that protesters set. Every officer who responded was pelted with rocks and other debris by the anti-Trump swarm, the department said.

Two juveniles were arrested and released to their parents, and a 30-year-old woman and a 19-year-old man were arrested and charged with disorderly conduct.

The department signaled that more arrests are likely but could not confirm reports that Mexican gangs were involved in stirring up the fracas.

Television news, already eager to cover Mr. Trump, has been filled with images of lines of officers preparing for violence and reporters documenting every rock-throwing incident.

Patrick Buchanan, a two-time presidential candidate, said the scenes could alarm moderate Republicans already wary of Mr. Trump, and there is a danger the protests could feed into a media narrative that he is inciting the violence.

For now, though, Mr. Buchanan said “on balance Mr. Trump wins” because the protesters appear to be backing up the candidate’s claims.

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