PEORIA, Ariz. — President Trump will make a campaign stop here Monday as a rapidly changing population puts a state that has not voted for a Democratic candidate for president in a generation at the forefront of the battleground map.

A new survey released Monday morning shows Trump in deep trouble in Arizona. The survey, conducted by Phoenix-based OH Predictive Insights, shows Democratic presidential nominee Joe Biden leading Trump by a 52 percent to 42 percent margin.

It is the eighth consecutive public poll that has showed the former vice president leading in Arizona, and Biden has led in 17 of the last 20 polls. A CBS News poll released Sunday showed Biden leading by a smaller 3-point margin, 47 percent to 44 percent.

OH Predictive Insights, a nonpartisan firm, has showed Biden leading Trump throughout the year, by between 4 and 10 points. In August, before either party convention, the firm found Biden ahead 49 percent to 45 percent. Biden’s current lead comes in a survey sample in which Republicans outnumber Democrats by 5 percentage points. 

The latest poll underscores the foundations of Biden’s lead over Trump, in both national and swing-state surveys: He is winning about the same percentage of voters as Hillary Clinton did in 2016 among groups that lean toward Democrats, but he is doing substantially better among groups that chose Trump over Clinton four years ago.

Biden and Clinton pull about the same percentage of Hispanic or Latino voters, 59 percent in the current poll and 61 percent for Clinton four years ago. But where Clinton lost white voters in Arizona by 14 points, according to exit polls, Biden leads by 6 among those voters. 

Clinton won female voters in Arizona by 9 points four years ago, and Biden holds a 12-point lead among them in the current survey. Among men, Trump won four years ago by 8 points; today, he trails Biden among men by 7 points, a 15-point swing.

Biden and Clinton hold support from almost identical shares of Democratic voters and moderates, a group that favored both Democrats by about 20 percentage points. Among independents, a group that tends to favor Republicans, Clinton lost by 3 points, according to exit polls; Biden leads the OH Predictive Insights survey among independent voters by 21 points. 

“Trump has a bit of a base problem. His base is less united. Biden’s is fully united, and independents are breaking heavy and hard away from Trump,” said Mike Noble, who conducted the OH Predictive Insights poll. 

Trump’s campaign dismissed the poll. In a call with reporters last week, campaign manager Bill Stepien said internal surveys showed Trump leading Biden by 2 points.

“This is not a serious poll, and it is not remotely accurate,” said Tim Murtaugh, the campaign’s communications chief. 

Arizona has long been safely in the Republican column. It has voted Democratic for president just once since Harry Truman’s landslide in 1948, and in that 1996 election Democrat Bill Clinton won just 46.5 percent of the vote, enough to win the state only because Ross Perot took almost 8 percent. Republicans held both the state’s Senate seats for 24 years, until Sen. Kyrsten Sinema (D) won her seat in 2018.

But below the surface, the state has changed substantially. Arizona has a booming tech sector, and a relatively inexpensive housing market that has attracted a new and younger generation of workers with more liberal views. 

Since 2000, Arizona’s population has grown by 50 percent, from 4.9 million to 7.3 million. Republicans enjoyed a 170,000-voter registration advantage in 2012; today, the GOP edge is 99,000 voters.

In Maricopa County, one of the fastest growing counties in America and home to 2 in 3 Arizona residents, about a third of the new residents who moved here in the last year have been from Pacific Coast states, according to Census Bureau data. 

“What’s had the biggest impact is the growth of young, urban, maybe some suburban white voters from places like California, Washington, Oregon. It’s made Maricopa County specifically much more purple in areas that didn’t used to be purple,” said Nathan Sproul, a longtime Arizona Republican strategist. 

Some Arizona political observers believe the last two Republican nominees before Trump effectively masked the demographic changes that were taking place. Sen. John McCain, the favorite son, beat Barack Obama in his home state by almost 9 points in 2008. Four years later, Mitt Romney beat Obama by 9 points, in part on his strength among the Mormon voters who make up about 5 percent of the state.

Both Biden’s campaign and Trump’s have made Arizona a key priority, a sign of its prominence at the fulcrum of American politics. 

Four years after Clinton committed $3.5 million to television advertising in Arizona, Biden had spent about seven times that much even before the Labor Day sprint to the finish line. Trump has spent $9 million here, more than any Republican nominee in recent memory.  

In an email, a Trump campaign spokeswoman said his team had maintained a presence in Arizona since 2016. The campaign said it had contacted voters 4.8 million, and that its meetup events had attracted more than 22,700 fans.

Arizona political observers say Maricopa is the key to either Biden’s or Trump’s hopes of winning the state, and perhaps the Oval Office. Only one candidate has won statewide office in recent history without winning the Phoenix-based county.

“Republicans have to win in Maricopa County by 6 to 7 points, as a general rule, and then hold down the losses in Pima County and have a big turnout in our rural counties like Yavapai and Mohave, some of those really strong Republican counties,” Sproul said.

In 2016, Trump won Maricopa County by 5 percentage points. Noble’s latest poll shows Biden leading there by an unprecedented 12 percentage points, 53 percent to 41 percent.

Noble warned Trump is running out of time — which may be why he is visiting Arizona on Monday.

“With early voting three weeks away, time is the most precious resource,” he said. 

The poll, conducted Sept. 8-10 among 600 like voters, carried a margin of error of plus or minus 4 percentage points.