The presidential campaign got fully underway this last week with a flurry of announcements, road trips and rallies that will roll across the country with increasing intensity for the next year and a half.
Most of what grabs headlines in the coming campaign will have little or no impact on who wins, past experience has shown. But underneath the hoopla, two clashing realities will shape what is likely to be a close and hard-fought battle.
Democrats will be trying to win a third consecutive presidential election, a difficult task made harder by the fact that by almost 2 to 1, Americans continue to believe the country is on the wrong track, polls show.
Republicans will be trying to win with a base of supporters that is roughly 90% white in an increasingly diverse country, having failed so far to develop a strategy to attract the growing minority populations who rejected them in 2008 and 2012.
Who wins will almost certainly depend on which proves more powerful — the hunger for change or the inexorable demographic wave.
Or to put it another way, the 2016 election will test whether the Obama coalition of minorities and white liberals can hold together, turn out and defeat the aging but still powerful coalition of social and economic conservatives and foreign policy hawks assembled by Ronald Reagan 35 years ago.
The best case for Republicans is that "the American public seldom has the stomach for a third term, and President Obama hasn't been the kind of leader who generates a third term," said political scientist Julia R. Azari of Marquette University in Wisconsin.
The two presidents in the modern era whose parties did win three or more elections, Reagan and Democrat Franklin D. Roosevelt, both transformed American politics by embodying — and helping bring about — a change in what people believed government should do.
Obama has not accomplished that. As a result, Azari said, for Hillary Rodham Clinton — or another Democratic nominee if she stumbles — it's hard to "talk about the Obama legacy" because it's not clearly defined.
Obama came into office with hopes of leading the country toward a new acceptance of activist government. Some Democrats hoped, for example, that successful implementation of the Affordable Care Act would cause Americans to warm toward the expanded government role in guaranteeing health coverage it represents.
Obamacare by now has helped more than 20 million Americans get insured, the biggest increase in coverage in half a century.
Contrary to dire warnings from the law's opponents, healthcare costs have not shot upward — the rate of healthcare inflation is the lowest in years — the job market has improved and the cost to the federal government is below forecasts.
Despite those successes, the country remains sharply divided on the law. American views of the Affordable Care Act have improved a bit in recent months — 43% disapproved and 41% approved in the most recent poll by the Kaiser Family Foundation in March — but mostly, opinions have been stuck about where they were when Congress first passed the bill in 2010.
Rather than changing the nation's close partisan divide, the healthcare law appears to have reinforced it.
Broader measurements also find continued widespread skepticism about government.
Last year, a poll by the Pew Research Center found 51% of Americans felt that "government is doing too many things better left to business and individuals," compared with 45% saying "government should do more to solve problems." The number on the conservative side has grown during Obama's tenure.
Combine those sentiments with the continued, decade-long feeling that the country is on the wrong track, and 2016 would seem a good year for a Republican presidential bid.
Maybe. The degree to which voters want change depends heavily on the state of the economy, said John G. Geer, political science professor at Vanderbilt University in Tennessee. As economic news has improved, so have Obama's poll standings, and Democratic chances in 2016 will rise to the extent that trend continues, he said.
Moreover, even if views of government's role have not shifted, something else has — with a strong impact on politics.
Under Obama, the Democrats have become even more firmly established in Americans' eyes as the party of tolerance and diversity. In a Pew poll taken in February, almost 6 in 10 Americans said the Democrats were "tolerant and open to all groups of people." More than 6 in 10 said the Republicans were not.
In the last two decades, the country's voting-age population has grown far more diverse, and acceptance of difference has become a more important value for Americans, particularly those younger than 50.
The change can be seen in the dizzying speed with which attitudes toward same-sex marriage have shifted.
An issue that Republicans used a decade ago to divide Democrats now cleaves their own party. GOP lawmakers in Indiana and Arkansas discovered that earlier this spring when votes to protect business owners with religious scruples against same-sex marriage backfired on them.
The degree to which Democrats are basing their appeal on that image of open-mindedness could be seen in the videotaped announcement that Clinton used to launch her presidential campaign last Sunday. The video said almost nothing about policy, but its montage of Americans of varied races, ethnicities and sexual orientations conveyed a clear message about diversity.
Republicans who doubt the power of that theme do so at their peril, warns GOP pollster Whit Ayres. In the last election, he notes, Obama lost among voters who said they most valued a president who is a "strong leader" or "has a vision for the future." But he won overwhelmingly among those who said they wanted a president who "cares about people like me."
Women and minorities have consistently rated the Republicans poorly on that dimension of political leadership, and Democrats have profited as a result.
Republicans continue to win big majorities among white voters, particularly men, people older than 50, frequent churchgoers and residents of the South. That support has enabled the party to win big victories in congressional elections, where older, white voters still predominate.
But in presidential elections, the white percentage of the electorate has shrunk steadily, from 88% when Reagan first won in 1980, down to 72% in 2012.
The white percentage has dropped as increasing numbers of Latinos, and more recently Asian Americans, have become voters. That trend will continue for decades as a diverse generation still in its teens reaches voting age and older whites pass from the scene.
What to do about that challenge has split Republicans.
Some party strategists argue that pushing just a bit harder will allow the GOP to squeeze one more victory out of the Reagan-era coalition. Obama voters, particularly blacks, may not show up as much without Obama on the ticket, they say.
Sen. Ted Cruz of Texas has been the most outspoken of the current Republican presidential hopefuls in declaring that nominating a combative conservative — one like him — would drive up Republican turnout.
On the other side of the divide, analysts like Ayres, who works for Sen. Marco Rubio of Florida, and Karl Rove, who was President George W. Bush's chief political strategist, warn that the GOP will lose, regardless of its 2016 candidate, if it fails to find a way to reach out to minority voters, especially Latinos.
"Trying to win a presidential election by gaining a larger and larger share of the vote from a smaller and smaller share of the electorate is a losing proposition," Ayres wrote in a recent book, "2016 and Beyond."
That sort of internal debate is typical of parties that have repeatedly lost presidential elections, Geer said. Often "the activists argue that the party was not pure enough in its values, and they push for a more extreme candidate who will be true to the party's ideology."
Eventually they usually get their wish, and it generally ends badly, he added.
"Ask [Barry] Goldwater or [George] McGovern," the 1964 Republican nominee and the 1972 Democratic nominee, Geer said. Both lost in landslides.