Protestors interrupted a major economic speech by Donald Trump at least a dozen timesby jumping up and shouting in a co-ordinated effort to disrupt the Republican presidential nominee's remarks.
One at a time, at least a dozen women seated throughout the audience stood up and yelled "Mr Trump", but their continued shouts were quickly drowned out by boos as security led them from the room.
An organisation called the Michigan People's Campaign said it was behind the protest. It was hard to hear the women, but the group said they were yelling at Mr Trump about jobs and his comments on women.
"It's all very well planned out," Mr Trump said after security had led several protesters out of the venue in Detroit.
In an apparently separate incident, one man also stood up towards the end of the event and yelled that Mr Trump has "tiny hands". That was believed to be in reference to a sexually-tinged comment by primary rival Marco Rubio.
Protesters have occasionally disrupted Mr Trump's larger rallies, where members of the public can enter. But this was the first time he faced such sustained resistance at a policy speech delivered to a private group.
He was speaking to the Detroit Economic Club and most people in attendance were club members or their guests.
Mr Trump largely stayed on message as security removed the protesters. He paused to let the disruption subside several times and occasionally continued speaking through protesters as the audience offered him applause and standing ovations.
"The Bernie Sanders people have far more energy and spirit," Mr Trump said after one woman was taken from the room.
Several audience members shouted "we love you, Trump" and other messages of support.
In his speech, Mr Trump outlined an overhaul of the income tax proposal he unveiled during the Republican primary campaign, increasing the amount that would be paid by the highest-income earners.
He said he wants to simplify the tax code to three brackets - 12%, 25% and 33% of income.
That is a change from September 2015, when he proposed four brackets that would pay zero, 10%, 20% and 25%.
Mr Trump said the "tax simplification will be a major feature" of his plan, and called it "the biggest tax revolution since the Reagan tax reform".
He insisted: "We will make America grow again."
Mr Trump is expected to roll out a series of new policy proposals in the coming weeks as he tries to steady his floundering campaign.
He has previously largely avoided policy specifics in his campaign, focusing instead on broad goals.
Mr Trump said he will unveil a proposal to reduce the cost of childcare and increase choices for parents.
He said he has been working on the plan with his daughter Ivanka, who is one of his top advisers.
Mr Trump also said he plans to lay out an education proposal that focuses on school choice, as well as one addressing law and order that would propose new funding and support for law enforcement officers.
Outside the Cobo Centre where Mr Trump was speaking, hundreds of protesters gathered.
Some held what appeared to be sections of white sheets with bricks and "No Borders" painted on them. Another sign read: "Trump Demeans Women".
A much smaller group of Trump supporters gathered nearby. One of their banners read: "Trump, Make America Great Again!"