Richmond, Virginia (CNN) -- Strategists for Barack Obama and Mitt Romney don't see eye to eye on much, but they do agree on this: It's tough to envision a path to the White House that doesn't include Virginia.And as they look for ways to tip the balance in November, an unlikely bellwether is emerging in the heart of Virginia: Henrico County, a longtime conservative bastion that has mutated into a key barometer for political watchers in the commonwealth.
"It's the battleground county in the battleground state," said state Sen. Donald McEachin, a Democrat whose district encompasses parts of Henrico. "When you look at Democratic success over the past few years, whether it's Tim Kaine, Mark Warner or the president, what they all have in common is, they carried Henrico."
The exception to that decade-long trend is Jim Webb, who narrowly lost the county during his successful Senate race against George Allen in 2006.
Henrico's swing status was affirmed in 2009, when Bob McDonnell wrested the county back into Republican control in the governor's race just one year after Obama won it during his march to the White House.
For operatives in both political parties, the county's shift from conservative to competitive is striking.
Along with Hanover and Chesterfield, Henrico is one of three populous suburban counties outside the heavily African-American city of Richmond that were long counted on to deliver big Republican tallies in statewide races.
Until Obama won Henrico in 2008 by a 56% to 44% margin over John McCain -- a result that echoed his 52% to 46% win statewide -- the county was a killing field for Democrats in presidential races.
George H.W. Bush swamped Michael Dukakis there in 1988 and did the same against Bill Clinton four years later. The county went for Bob Dole over Clinton in 1996. George W. Bush won Henrico twice.
The county, the fifth largest in the state, is steeped in history and conservative tradition.
Founded in 1611 and named for Prince Henry, the typhoid-stricken eldest son of King James I, Henrico was one of the Virginia colony's eight original "shires": a point of pride for locals.
Today, tidy neighborhood roads are dotted with state-funded "Historical Highway Markers" that highlight minor Civil War skirmishes like "Dahlgren's Raid" and more momentous events like "Stuart's Mortal Wound."
Public schools bear the names of Harry F. Byrd, the towering founder of the Byrd Organization who ruled the state's politics for decades, and Mills E. Godwin, who helped Byrd implement the infamous program of "massive resistance" to school desegregation.
One high school, Douglas Southall Freeman, is named for Robert E. Lee's Pulitzer Prize-winning biographer. Its mascot is the "Rebel," though students long ago stopped waving the Confederate battle flag at football games as the school band played "Dixie."
Over the past 20 years, demographic shifts, steady growth and a burgeoning African-American population on the county's eastern side have transformed the county politically.
Affluent white voters are increasingly opting to settle in Chesterfield or Hanover instead. Out-of-state newcomers, known locally as "come-heres," have arrived in large numbers, further diluting Henrico's conservative flavor.
"It's gone Republican, and it's gone Democrat, and it's because there is a big group of independents who will vote the person and vote the issue, and where those independents go, that's where the elections go," McDonnell said.
African-Americans now account for a third of Henrico residents, up from 20% two decades ago, according to census data.
"Henrico is now more divided east and west than it's ever been," said Ray Allen, a veteran GOP consultant in Richmond. "And the reason for that, if you actually look at the voter trend, it's the growth in the east end of Henrico. It's now more minority than it ever was.
"Obama won Henrico in 2008 because he did very well in the east end," Allen said. "Bob McDonnell did really well in the 2009 governor's race because he was winning all the Republican areas in the west end and those swing moderates, the suburban vote."
The geographic and racial divide is reflected in the state's congressional map.
The west end of Henrico falls into the 7th District, represented by House majority leader and staunch conservative Eric Cantor.
The east end is carved into Rep. Bobby Scott's majority-minority 3rd District.
But the racial makeup is more complicated than just black and white. A swelling immigrant population in Henrico includes not just Latinos but emergent Vietnamese, Cambodian, Indian and Bosnian communities.
Democrats and Republicans alike say the area is increasingly taking on the character of the rest of the state.
"On election night, I want to know what Henrico is doing," said former Attorney General Jerry Kilgore, a Republican who lost the county to Kaine in the 2005 governor's race. "It's really gone from red to purple in the last five to seven years. As Henrico goes, I think, the state will go in the presidential race and the Senate race, mainly because of the diversity in the county."
Levar Stoney, a Democratic operative advising likely gubernatorial candidate Terry McAuliffe, said the county has a little bit of everything: moderates, conservatives, liberals, blacks, evangelicals, business types and more.
"It's a cross-section of Virginia," he said. "If you find out what the vote total is on election night in Henrico, you will probably have a good idea of where Virginia is on election night as well."
The changing face of Henrico is a prime reason Obama's campaign in Virginia is once again targeting the area aggressively.
The campaign has two organizers dedicated to Henrico County: one for the predominantly black east end and another for the west end.
At the opening of their Henrico field office Saturday -- it's the Obama campaign's 15th office in the state -- organizers told a group of about 60 volunteers, most of them women, that the work ahead of them will be even more daunting than it was in 2008.
Since McDonnell's convincing victory two and a half years ago, Virginia Republicans have built the kind of sophisticated voter contact operation they sorely lacked during the last presidential race.
In big counties like Henrico, GOP turnout is expected to be markedly higher than it was when Obama won the state.
That leaves the Obama team with the difficult task of re-energizing supporters from the previous campaign along with identifying new voters, all while convincing skeptical independents who have retreated from Obama over the last three years to come back into the fold.
Lise Clavel, Obama's state director in Virginia, told the Henrico volunteers in stark terms that the campaign is certain to be outspent in the commonwealth by Mitt Romney and his allies.
"They are getting laser focused on Barack Obama now," Clavel told the group. "Those guys are coming after us, and they are coming after us hard."
Bridgit Donnelly, one of the campaign's regional field directors, echoed the warning as she tried to sign up neighborhood team leaders for Obama.
"This is going to be a huge fight to make sure we can turn Henrico blue again in November," she said.
