If the 20 Democratic candidates headed to Detroit for the July 30-31 debates are serious about becoming president next year, here's some advice: Stop in Sterling Heights.

Or Clinton Township. Or Fraser. Or just about anywhere south of Hall Road, that informal demarcation line between more solidly Republican townships to the north and somewhat more Democratic ones in the closer-in suburbs in Macomb County.

Politically speaking, this is the promised land.

"We vote for Republicans sometimes and sometimes we vote for Democrats," said Sterling Heights Mayor Michael Taylor. "I'd say 20% to 25% on each side are only going to vote for Republicans or Democrats (all the time). That leaves a pretty big middle."

Working-class, mostly white and the third-largest county in Michigan, Macomb County has been and remains a political enigma. Stretching from mostly Democratic enclaves along 8 Mile in Warren and Eastpointe to overwhelmingly Republican rural townships to the north, it is also hugely predictive, having picked the statewide winner for governor or president in the last seven elections and in all but three of the last 20.

That's in a state that has elected Democrats 11 times, Republicans nine. And with Michigan very much expected to be a swing state again in 2020's presidential election, candidates of both parties would be wise to pay attention to it.

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Typically, Macomb County accounts for only about 8%-9% of the statewide vote, compared to about twice that for Democratic-leaning Wayne County. Yet it often has as much — if not more — impact on the outcome. And just as pundits try to declare it one thing — as when it backed President Barack Obama in 2008 and 2012 — it changes course entirely, as it did with Donald Trump in 2016.

"It's been that way for a long time," said former U.S. Rep. David Bonior, D-Mt. Clemens, who represented the county in Congress for 26 years. "They’re looking for something different that might work."

But unlike a lot of counties in Michigan, Macomb County defies easy explanation: As most others trend one way or another, it doesn't. And yet, Trump understood better than anyone in 2016 how important it was: Two days before the election, he drew a standing room-only crowd to Freedom Hill Amphitheater in — you guessed it — Sterling Heights.

So what should this Democratic group of candidates know about Macomb County? Here it is in a nutshell.

Voters in Macomb County fiercely independent

More than anything else, Macomb County — taken as a whole — likes to show its independence and often veers wildly in terms of which party it supports overall, unlike most counties. And while Democrats more typically have been more successful in presidential years and Republicans in gubernatorial ones, that is by no means certain.

Consider the most recent elections: Obama won handily a second time in 2012, beating Michigan-born Mitt Romney by 4 percentage points, only to see Hillary Clinton — whose husband, Bill, won Macomb in 1996 — lose to Trump by 12 percentage points, a massive 16-point shift. Likewise, Republican Gov. Rick Snyder won easily in 2010 and 2014, only to see Democrat Gretchen Whitmer win by 4 percentage points last year over Bill Schuette, a 14-point shift.

County all over the map in its voting preferences

The close-in suburbs — Warren, Center Line, Roseville, Eastpointe — are pretty solidly Democratic, especially in presidential years, and taken as a group they gave Clinton a 14-point edge over Trump in 2016. That was similar to the margin they gave Democratic gubernatorial nominee Mark Schauer over Snyder in 2014.

But those suburbs account for only about one-quarter of the total vote in Macomb, while the area north of Hall Road — which includes Shelby Township, Chesterfield Township, fast-growing Macomb Township and more — accounts for more than one-third and is predominantly Republican. As a group those townships and cities gave Trump a 64%-32% edge over Clinton in 2016, which was far better even than the 58%-42% edge they gave Romney over Obama in 2012.

That leaves the suburban area between the two — Sterling Heights, Clinton Township, Fraser and St. Clair Shores, accounting for more than 35% of the vote — to swing the outcome.

And swing it has...

Looking at the 11 presidential or gubernatorial elections going back to 1998, that middle ground has moved back and forth between the parties seven times. In each case, it has also predicted which party would win the county. In all but two — Jennifer Granholm's win as governor in 2002 and John Kerry's Michigan win on his way to losing the 2004 election for president — it predicted the statewide outcome.

And that's true not just as a group but individually.

Both Clinton Township and St. Clair Shores, while clearly leaning slightly more Republican on average in those elections, still swung decisively toward the Democratic candidate in several of those years, including Obama's two elections and Whitmer's last year. As for Sterling Heights — which is the state's fourth-largest city and competes with Warren for the largest vote total in the county — it has augured the outcome for the rest of Macomb County in every one of those elections since 2002.

But what explains the swing?

As with many of the Detroit suburbs, there has been a persistent argument that racial politics play an oversize role in deciding Macomb's elections. And certainly, the old image of "Fortress Warren," in which leaders in that city talked about walling off crime — and presumably residents — of majority black Detroit persists, as do allegations of racism.

Sterling Heights, still predominantly populated by whites, has at times been referred to as "Sterling Whites," say some who lived there.

But if anything, Obama's victories in many of those communities — not once, but twice — argue against that. So does the fact that, while Macomb is the whitest of the three metro Detroit counties, the percentage of white residents has fallen precipitously — from 93% in 2000 to 82% in 2017, the steepest such drop in the state.

And unlike other counties, Macomb refuses to be easily characterized. For instance, the Free Press in previous coverage has shown how counties in which growth rates have slowed are trending more Republican while those that are expanding are trending more towards Democratic candidates in statewide elections. But Macomb has grown by about 11% over the last two decades and still maintained its fickle nature in deciding top elections.

The county remains hard to define

Other factors don't explain it either. Average age is up, but not out of line with most other Michigan counties; the percentage of Macomb County residents with a bachelor's degree or higher — 24% in 2017 — was 7 percentage points higher than it had been and was higher than most counties, including Wayne.

In 2017, household median income was $58,175 — not as high as Oakland ($73,369) or Livingston ($78,430) but still the 11th highest among Michigan's 83 counties. And while manufacturing jobs are down over the last 20 years, that's true pretty much everywhere in Michigan.

"If you look at income levels, that independent vote crosses over all sorts of income levels," said Melissa Roy, a public affairs consultant who worked for County Executive Mark Hackel, a Democrat who, in true Macomb County form, has been willing to endorse Republican countywide candidates. "It's not limited to a certain demographic. It cuts just about everybody’s income level."

Instead of looking at the county or even parts of the county as monolithic, she said, you have to realize that in relatively close proximity you have people with different styles of living: urban, suburban, rural. But even that is not necessarily predictive: In Sterling Heights, for instance, the precincts with the largest switch from backing Obama in 2012 to backing Trump in 2016 came from places at both ends of the income scale.

Ultimately, it may come down to candidate personality

Political watchers tend to talk about Macomb's blue-collar history, its union connections. And it's true: All three domestic automakers have a presence in the county as do lots of suppliers. The auto industry employs more than 35,000 people in Macomb County. And, according to Stan Greenberg, a Democratic pollster and researcher who famously studied the so-called "Reagan Democrats" of Macomb County, the white working-class voters there still respond to a candidate, like Trump, who they see as "no nonsense," who "doesn't sugarcoat" the problems they see facing America such as illegal immigration and overseas competition.

While it's impossible to quantify, many people who know Macomb County's politics intimately say voters there are more likely to respond to a strong personality than they are to lengthy policy statements.

And there is some recent evidence to support that. Putting aside their vast political differences, both Obama and Trump campaigned in stark, personal terms and represented almost larger-than-life political forces. And it doesn't stop with them.

Snyder, a political neophyte, campaigned less as a Republican than as a self-proclaimed "nerd" with a message. Whitmer starkly demanded that Michiganders set aside politics and "fix the damn roads."

"It's a lot less partisan in Macomb County," said Democratic political consultant Joe DiSano, who grew up in Chesterfield Township. "It's rarely about issues. It's usually about personalities. They tend to respond to folks who are a little more vibrant, a little more outspoken."

Roy said you also see a lot of what she calls the "not that guy" vote: Residents voting against someone who doesn't grab them in some way. "It was the same thing (for Obama) in '08 and '12 ...and you have it in '16 with Clinton (when Trump won.)"

It certainly seems true that Macomb County voters were less turned off by their presidential choices in 2016 then in some other counties: In both Wayne and Oakland counties, the number of voters showing up at the polls who still didn't vote for president more than tripled (and in Wayne nearly quadrupled) compared to 2008. In Macomb, it didn't even double, going from 3,142 to 5,367.

So who will win and how?

Some pundits, like DiSano, feel that Macomb is prime territory for someone like Vice President Joe Biden, who has longstanding connections with blue-collar communities and labor. His stances — more moderate than much of the big field — could help him there. He's also been a close and longtime friend to U.S. Rep. Debbie Dingell, D-Dearborn, and her late husband John, the longest-serving congressman in U.S. history, who together for decades were the first family of Democratic politics in Michigan.

Others seem to think it's for the taking.

Surprising no one, U.S. Sen. Bernie Sanders of Vermont went to Warren in April, attracting more than 1,000 people at Macomb Community College. And while Sanders' progressive platform — government-run health care and strict environmental control — may run counter to what some might see as playing well in the county, it's worth noting that Sanders, who eked out a primary win against Clinton in 2016 in Michigan, isn't lacking in the personality department.

Bonior, meanwhile, is working with U.S. Sen. Elizabeth Warren of Massachusetts and thinks that her long list of policy proposals — and her "I've got a plan for that" wonkiness — is going to play better than some might expect in Macomb. "She's very thoughtful, tough and caring," he said.

State Sen. Michael MacDonald, R-Macomb Township, whose district includes Sterling Heights, says he doubts that a message that suggests to voters that government is going to do everything for them will play in his county and believes that an economic message about jobs and opportunity is what will pay off.

But he acknowledges that "it really isn't (about being) Republican or Democrat" but about personal contact and about listening what their concerns are.

"If you're a good candidate, they're going to vote for you. If you're not, they're not."

MacDonald is and remains a Trump supporter and believes that, whomever the Democrats nominate, Trump will carry Macomb again.

Sterling Heights Mayor Taylor — whose job is nonpartisan but who considers himself a Republican — isn't so sure. He voted for Trump in 2016, and believes that Trump spoke more to the working-class voters in his city than Hillary Clinton did. And he's got his doubts about anyone who promises huge government programs winning support in the county.

But he won't vote for Trump again.

"I voted for him and I regret it," Taylor said, referencing Trump's Twitter insults, the way he speaks of others. "He’s not someone I want my kids emulating. ... Even if he were full of good picks and good policies, I can't condone it. I know of a lot of people who feel the same way."

He says as mayor he's met one of the Democratic candidates, though: South Bend Mayor Pete Buttigieg, who has seen his standing rise, and who seems to be taking a more moderate tack than many in the race for the nomination.

"He's able to keep his calm and really explain things .... I think he’s got more than just a shot," he said. "I think he’s got to get to places like Michigan and Wisconsin and talk about his Midwest roots."

"I’d love to invite him to Sterling Heights to meet our voters."

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Contact Todd Spangler attspangler@freepress.com. Follow him on Twitter@tsspangler. Read more onMichigan politics and sign up for ourelections newsletter.