The second debate for top Republican presidential candidates included bashing Donald Trump, a fiery Carly Fiorina and an admission from Jeb Bush that he says his mom won't like. (CNN)

To the Democratic candidates, the 2016 presidential campaign is about shrinking the gap between rich and poor; combating climate change; and expanding voting rights, gay rights and workplace equality for women.

To listen to the Republican candidates is to hear an entirely different campaign — one that centers on defeating Islamic State terrorists, deterring a nuclear Iran, restricting abortion, and debating whether to deport illegal immigrants and construct a wall to keep them out.

At a political moment of pitched voter anxiety, candidates in both parties talk in dark, sometimes apocalyptic tones — but about different issues, as if they’re addressing two different countries.

“Republicans are from Mars, Democrats are from Venus,” Republican strategist Ari Fleischer said. “The gulf between the two parties has grown wider in the last decade, not smaller.”

For Sen. Bernie Sanders (I-Vt.), vying for the Democratic nomination, it’s the corporate billionaire class that is destroying America by crushing the dreams and livelihoods of working people. For many Republicans, the rise of new threats abroad and cultural changes at home are destroying America by shaking its foundation.

Hillary Rodham Clinton, seen campaigning Sept. 7 in Hampton, Ill., focuses chiefly on economic and family issues in her stump speeches. (Melina Mara/The Washington Post)

The contrast was brought into sharp relief this week. Republicans sparred in a three-hour debate Wednesday over issues of national security, abortion and immigration, but had little to say about middle-class economic growth. On the campaign trail, Democrats focused on liberal economic and social agendas, but barely touched on terrorist threats and the cultural issues that have become conservative rallying cries.

David Winston, a Republican pollster unaligned in the presidential race, said the economy is the top issue for all voters. “Whenever the candidates are not talking about jobs and the economy, they’re off on the wrong topic,” he said.

Some difference in emphasis is to be expected, considering that each party’s base voters are animated by different issues. At this stage in the race, the candidates are playing to those bases in an attempt to win the nomination. But the gulf in the 2016 campaign has grown particularly noticeable.

James Pethokoukis, a scholar at the American Enterprise Institute, a right-leaning think tank, studied the transcript of Wednesday’s prime-time GOP debate. He found 10 references to the Middle East and four to the middle class; 23 to defunding Planned Parenthood and three to single parents; seven to a border wall and five to economic growth.

“As a casual viewer watching this show, what did they get out of it? They got, once again, a Republican Party that doesn’t have much to say about their concerns,” Pethokoukis said. “What should be the core Republican themes — growth and opportunity, upward mobility — didn’t get much play. There were 11 on stage, and they could’ve seized control and talked about these things, but it didn’t happen.”

Some Republican strategists said they were frustrated that the debate moderators did not ask questions about a broader array of subjects, though CNN had signaled in advance that the debate would focus heavily on foreign affairs. And they said comparing what Republicans say in answering questions at a debate with what Democrats say in their stump speeches is unfair.

Voters listen as Hillary Rodham Clinton gives a speech at a Labor Day chicken fry in Hampton, Ill. (Melina Mara/The Washington Post)

Peter Wehner — a senior fellow at the Ethics and Public Policy Center who, along with other conservative reformers, has attempted to make the GOP more empathetic by focusing on economic mobility — said he worries that the narrative coming out of the debate could be damaging.

“I shook my head, thinking, ‘Oh, my gosh, we’ve spent 20 minutes talking about birthright citizenship,’ ” Wehner said. “But it’s a product of the questions that were asked. Marco Rubio would love to talk about college affordability and student debt. And Jeb Bush, I don’t know that there’s any issue he’d rather talk about than social mobility.”

Sanders and Democratic rival Hillary Rodham Clinton seized on the differences to paint Republicans as out of touch with the electorate. During the debate, Sanders tweeted: “Waiting, waiting, waiting. Will we hear anything about racial justice, income inequality or making college affordable?”

Clinton campaign manager Robby Mook told reporters assembled at her New York headquarters on debate night: “Carly Fiorina got her biggest applause when she went on a tirade against Planned Parenthood. . . . They have a completely out-of-date and out-of-touch philosophy. It’s hard for me to see through their prism on some of these things.”

On Friday, Clinton told a crowd in Durham, N.H.: “You’ve got to understand, this is an ideological divide. Let’s make no mistake about it.”

Joel Benenson, Clinton’s chief strategist and pollster, said in an interview that by running in what he dubbed “the Fox News network primary,” the Republican candidates are alienating working- and middle-class voters.

“At the moment, it certainly seems that the Republicans are talking to a more narrow slice of America,” he said. “I’m not going to say it’s two different Americas because I think we’re one country, but they are talking to the base of their party, not a broader swath.”

Economic and family issues such as college affordability, the minimum wage, executive compensation, early child care and paid sick days that have formed the foundation of the Clinton and Sanders campaigns have largely been absent in the Republican discussion. Benenson said that this is a mistake and that Clinton and her campaign will try to exploit it.

“If you’re not addressing it, that’s your choice, and that’s what the Republicans are doing,” Benenson said. “They are missing the mark on what’s really affecting people’s lives and what people care most about.”

Some Republican candidates have tried to emphasize these issues, however.

Bush has sought to frame his campaign around lifting up the middle class, with “right to rise” as his slogan. Last week, the former Florida governor unveiled a sweeping tax reform plan that he argues would help spur annual economic growth of 4 percent. But it got relatively little media attention, overshadowed by front-runner Donald Trump’s continuing feuds with Bush and Fiorina, a former Hewlett-Packard executive.

“Jeb’s whole campaign is all about economic growth. . . . He rolls out the most significant piece of his plan to get us rolling at 4 percent, and it’s ignored. That’s unfortunate,” Edward Lazear, who served as President George W. Bush’s chief economic adviser, told a group of reporters this week at the Hoover Institution at Stanford University.

At Wednesday’s debate, some candidates became visibly irritated by the focus on what they considered diversions from the core concerns of middle-class voters.

“Listen,” New Jersey Gov. Chris Christie fumed. “While I’m as entertained as anyone by this personal back-and-forth about the history of Donald and Carly’s career, for the 55-year-old construction worker out in that audience tonight who doesn’t have a job, who can’t fund his child’s education, I’ve got to tell you the truth.

“They could care less about your careers,” he continued. “They care about theirs. Let’s start talking about that on this stage and stop playing games.”

John Wagner in Durham, N.H., and Anne Gearan in New York contributed to this report.