The year 2015 will long be remembered as the year of Donald Trump. (Scott Eisen/Getty Images)

The election year has started as 2015 ended, only more so. If campaigns are always about the future, the 2016 one points to a country that could end this year even more divided against itself than it was after the 2012 election.

The year 2015 will long be remembered as the year of Donald Trump, all the more so because of the unexpectedly strong response his candidacy set off. Other Republican candidates once hoped they could ignore the meaning of Trump’s appeal and ride along their own track. Some still think that way, but in reality, all have been subsumed into Trump’s world, even if not his worldview.

The other Republican candidates, particularly those in the mainstream conservative wing, now appreciate, as they might not have before, how much they are dealing with an electorate fed up with Washington and the Republican Party’s leadership, with economic dislocations that have affected the working and middle classes, and with resentment toward cultural shifts that reflect the diversity and tolerance of a changing country.

Trump’s rivals have begun to channel some of that anger, and it has given a different tone to the Republican race than existed even a few months ago. “I recognize people’s frustration, and you’ve got to speak to that,” Sen. Marco Rubio (Fla.) said in a pre-New Year’s Day interview. “If they don’t believe you’re in touch with what they’re feeling in their lives, there’s no way they’re going to make you president.”

There’s still some optimism left in the messages of Republicans such as Rubio, but mostly it has been subsumed in a chorus of angry rhetoric, a sense of foreboding about threats of terrorism and the rise of the Islamic State, petty attacks against one another and harsher criticism of President Obama.

The more the Republican candidates have amped up their rhetoric, the more they have triggered a sharp response from the Democrats. Hillary Clinton, who said last fall that she is proud to think of Republicans as enemies, never seems happier on the campaign trail than when she is denouncing the other party as one captured by extremists.

It’s natural at this stage of any campaign, as the first votes in Iowa and New Hampshire near, for the candidates to be speaking to their own party loyalists and not to the country as a whole. In a polarized country, energizing the base of the party is a prerequisite to winning the nomination, if not the general election.

More so than in some past campaigns, however, the effect of all this seems to be accentuating the gap between left and right, between Democrats and Republicans, between elites and the rest of the population. That is likely to continue well into the spring as the GOP candidates try to settle their nomination contest.

For now, there is nothing to pull anyone in the GOP field back from this pell-mell dash into the politics of anger. Between now and mid-March (and possibly beyond), attacks could overwhelm everything else. And in the first days of 2016, attacks and attack ads underscored how little any of the candidates knows about where the race is heading.

The party is in turmoil, most especially the establishment wing. Party elites are alarmed at the prospect of either Trump or Sen. Ted Cruz (Tex.) as the nominee, even as they reassess what they once thought of as the minimal chance that either could win that prize.

The establishment candidates — former Florida governor Jeb Bush, New Jersey Gov. Chris Christie, Ohio Gov. John Kasich and Rubio (who claims to wear the establishment label reluctantly) — are in a food fight with one another. All now think that they have a chance to emerge as the dominant candidate who will go on to contest for the nomination against Trump, Cruz or both later this spring.

These establishment candidates started the year in a circular firing squad with a barrage of attacks — both verbal and in TV ads — that could leave all of them badly damaged by the time it’s clear which of them emerges as the strongest after voters in the first few states have their say. It is the reverse of the traditional pattern in which the establishment coalesces early and the insurgent candidates are left to fight for survival.

Christie, Rubio, Bush and Kasich have traded barbs and insults that will only become louder in the next few weeks. Earlier, Rubio and Cruz were combatants, anticipating a potential showdown for the nomination. Now Rubio and Christie are tangling. Christie attacks Rubio as callow and weak, not the kind of candidate who can go toe-to-toe against Clinton in the fall. Rubio fires back that Christie has a record pock-marked with views anathema to the Republican base. Bush has become the most consistent anti-Trump voice in the field.

Meanwhile, Trump regularly and strategically drops grenades into the race, forcing the conversation in unanticipated, divisive and sometimes diversionary directions. He did it late last year with his call for a halt, at least temporarily, on the entry of Muslims into the United States. He did it again last week when he spoke publicly about whether Cruz, who was born in Canada to an American mother, is a natural-born citizen and therefore eligible to be president.

That’s the state of things for now and probably for the foreseeable future. What’s missing is vision. Is there any candidate in either party with a big, positive and hopeful message that looks over the horizon at the challenges to come, particularly one that has broken through? Some might argue that Sen. Bernie Sanders (I-Vt.) is that candidate, but the force of the energy behind his surprising candidacy is grievance toward banks and billionaires and other elites.

As the year begins, most candidates are selling fear of the apocalypse, stark warnings about what happens if the other party wins in November. Some, like Trump, are playing to darker sentiments. In these early weeks, the seeds are being planted for a general election that inflames rather than unites, that hardens the divisions that already exist rather than the opposite.