This column takes its name from its intention: it aims to explore the fault lines in American society and politics.

It is not designed to illuminate politics from the inside out, with tales of backroom maneuvering. Instead its goal is to track American politics from the outside in. It aspires each week to chart how economic, demographic and cultural change is reconfiguring the American electoral landscape -- and how the parties are responding to those changes in their agenda and strategy.

Years of unrelenting, even accelerating, change in our economy, culture and demography have carried the US into an era of polarized, fierce, and volatile politics.

In the past several decades the country has hurtled through a succession of demographic milestones. In 1980, when Ronald Reagan was first elected, members of minority groups represented only about one-fifth of the US population. That share has now roughly doubled . The change is especially pronounced among the young.

Demographers project that kids of color will comprise a majority of all Americans under 18 soon after 2020; they already represent a majority of the under ten population and the K-12 student body in America's public schools nationwide.

The tide of change has swept away other certainties. Through most of American history, whites without a college education -- from Thomas Jefferson's yeoman farmer to Henry Ford's assembly line worker --- constituted a majority of the US population. But with increasing diversity and rising education levels, those working-class whites fell below half the population for the first time around 2004 and have continued to shrink as a share of both adults and voters. Both media exit polls and US Census Bureau data showed that despite Trump's magnetic appeal for whites without a four-year college degree, those voters continued their long-term decline as a share of the electorate last year.

Similarly, after representing most Americans for almost all of the nation's history -- and nearly 7 in 10 as recently as 1984 -- white Christians fell below majority status around 2012, survey data show. Though white Christians remain the largest religious group in America, they are now just one strand in a complex tapestry that includes a proliferation of faiths and an increasing number of Americans who align with no organized religion.

Economic change has been equally unstinting. The decline of manufacturing employment, the rise of service work, and the disruptive ripple of growing globalization, automation and digitization through every segment of the economy have produced opportunity and disruption in equal measure. A slowdown in the growth of living standards for average families (especially those without advanced education), widening inequality of income and wealth, and the concentration of economic opportunity into a relative handful of superstar metropolitan areas (only decades after the nation's cities were seemingly left for dead in the 1970s) have all generated unease and uncertainty alongside optimism and opportunities.

Cultural change has come just as fast. Marriage, work and parenting continue to be redefined in the shifting arrangements that men and women negotiate every day in an unending process of social reinvention. Newlyweds are now over five times as likely as in the 1960s to be married to a spouse of a different race or ethnicity . In just years, same-sex marriage hurtled from a vanguard idea among a few theorists to the law in every state. Transgender rights have become the newest, but surely not the last, frontier of cultural conflict.

Taken together, these changes have produced a kaleidoscope society defined by the absence of any single dominant racial or religious group. In this maelstrom, neither party has successfully established a lasting advantage: the unified control of the White House and both chambers of Congress that Republicans enjoy now has become much more rare over the past half century than in earlier generations. (Since 1968, neither party has sustained unified control of government for more than four consecutive years, far greater turnover than was common earlier in the 20th century.)

And while neither party has pulled away from the other in the electoral competition, they have, emphatically, pulled apart. For most of our history, American political parties were ramshackle coalitions of diverse and even contradictory viewpoints. Today each side is much more ideologically homogenous. This resorting has narrowed the differences within the parties, but widened the distance between them. Congress has become a quasi-parliamentary institution, where the two sides now routinely line up shoulder-to-shoulder against each other like armies during the revolutionary war.

Both demographically and geographically, the parties now represent virtually mirror image Americas with very little overlap. (Sixty percent of us live in landslide counties that were decided by at least 20 percentage points in last fall's presidential race, far more than decades ago .) Democrats rely on an electoral coalition that is more racially diverse, younger, more secular, overwhelmingly urbanized, and more rooted in the globalized, post-industrial and low-carbon economy. Republicans, in turn, mobilize a coalition that remains preponderantly white, older, more religiously devout, dominant almost everywhere outside of the major metropolitan areas, and strong in communities that rely on manufacturing and the extraction of resources, especially fossil fuels.

Not everyone who supports each party, of course, fits into those categories. But years of shifting political allegiance has replaced the primarily class-based political alignment of the decades immediately after World War II with a new cleavage centered on these economic, cultural and demographic changes remaking America.

That jagged contrast between what I have called the Democrats' "Coalition of Transformation," which largely welcomes those changes, and the Republican "Coalition of Restoration," which largely feels unsettled or eclipsed by them, has become arguably the central fault line in American life.

It is along that fracture that America's most fierce political conflicts are unfolding -- and where the opportunities to bridge our differences may eventually be found. That contested ground is the terrain this column will attempt to map. I hope you will join me every week on that journey.