Protesters blocked a main road leading to the Phoenix suburb where Republican presidential front-runner Donald Trump staged a campaign rally days ahead of the Arizona primary.
Tempers flared at the rally, but without the violence that marred Mr Trump’s event in Chicago a week earlier.
He never goaded the protesters as he usually does at campaign events.
For hours, about two dozen protesters parked their cars in the middle of the main road to the event, unfurling banners reading “Dump Trump” and “Must Stop Trump”, and chanting “Trump is hate”.
Traffic was backed up for miles, with drivers honking in fury.
The road was eventually cleared and protesters marched down the road to the rally site, weaving between Trump supporters who booed and jeered them.
Mr Trump was in Arizona to campaign ahead of Tuesday’s primary in which the winner will take all 58 delegates at stake.
Polls show him leading his rivals in the border state where his hard line on immigration has drawn support from Republican voters.
Mr Trump was introduced at the rally by Joe Arpaio, the tough-talking sheriff of Maricopa County, which includes Phoenix and nearly two-thirds of Arizona’s population.
Mr Arpaio has supported harsh measures to deal with immigrants living illegally in the US. He has forced inmates to wear pink underwear and live outside in tents during 38C-plus heat.
Mr Trump’s main rivals, Ted Cruz and John Kasich, are desperately trying to prevent the real estate mogul from accumulating the 1,237 delegates needed to secure the nomination at the party’s national convention in July.
They are hoping for a contested convention in which delegates would be freed to turn from Mr Trump if he failed to win a majority on the first ballot.
He has won 678 delegates so far. Mr Cruz is in second place with 423 delegates, and Mr Kasich is third with 143.
His rivals hope to offset a likely Trump win in Arizona on Tuesday with a strong showing in the Utah caucuses, where Mormons account for two-thirds of the state’s three million residents.
Limited polling shows Mr Trump running second to Mr Cruz, but ahead of Mr Kasich, said Jason Perry, director of the Hinckley Institute of Politics at the University of Utah.
The delegates will be distributed according to percentage of votes – unless a candidate gets more than 50%, which would give that person all 40 delegates.
Mitt Romney, the 2012 Republican presidential nominee and the Mormon faith’s most visible member, said he intends to vote for Mr Cruz in the caucuses, but stopped short of endorsing the Texas senator, an uncompromising conservative.
In Arizona, thousands of Trump supporters gathered for the outdoor rally in the Phoenix suburb of Fountain Hills where Mr Arpaio lives.
Officers with the sheriff’s department were posted throughout the park, on rooftops and on patrol.
Some had feared that the event in Fountain Hills could descend into violence reminiscent of last week’s rally in Chicago, which was cancelled over safety concerns.
Confrontations involving protesters, Trump supporters and police have become standard at his rallies across the country.
Later in Tucson, dozens of protesters made their way into another Trump rally and interrupted him as he spoke.
In typical form, he had the protesters kicked out, but urged the crowd of about 1,000 people to be nice to them.