With voters divided between Republican Donald Trump and Democrat Hillary Clinton on perennial top issues such as the economy and national security, undecided and unmotivated swing voters in this close campaign between candidates with high unfavorable ratings will increasingly be targeted through narrower wedge issues such as race, abortion, gun control and climate change, according to researchers.

“We talk about likability and personal appeal, but in this election, policy appeal may ultimately be more persuasive than personal appeal,” said Meena Bose, executive dean of Hofstra University’s Program in Public Policy and Public Service and director of the Peter S. Kalikow Center for the Study of the American Presidency.

“When the swing states matter and in an election when every vote counts . . . and the person isn’t going to bring a voter out, maybe an issue will,” she said. “It may make a difference.”

Last week, a traditional wedge issue plied by each party for decades exploded.

Clinton told CNN on Thursday that Trump was “taking a hate movement mainstream.” Trump in turn called Clinton a bigot.

Trump has been accused of using what political scientists call “dog-whistle” statements aimed at wedge voters, but carefully phrased to avoid alienating most Americans, researchers say.

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Steven Greenberg of the Siena College Research Institute said this election, in which candidates have the highest unfavorable ratings in generations, is primed for wedge issues from the left and right.

“Immigration and gun rights are two issues that Republicans hope will help boost support for Trump, while a woman’s right to choose and climate change are issues that Democrats hope will attract voters to Clinton,” he said. “The future of the Supreme Court is an issue that both sides are using.”

“This year there is a motivating factor of strong dislike for the candidates,” said political scientist Lee Miringoff, who directs the Marist College poll. That, he said, creates fertile ground for wedge issues in direct attacks and in dog-whistle attacks. “Probably the ultimate wedge issue will be their Supreme Court appointments . . . both will posit their opponent as a threat to the democracy and progress, the Second Amendment versus women’s rights.”

Throughout the campaign, Clinton has accused Trump of planning to ban abortion, which is a top issue for many liberals; and Trump has accused Clinton of planning to abolish the constitutional right to bear arms, which is a top issue for many conservatives. Each candidate denies the accusations against them.

Stanford University Professor Morris Fiorina said wedge issues could motivate some voters. “The problem is that we don’t know how many” there are, Fiorina said.

No one is sure how big this group of unmotivated and undecided party members and independent swing voters will be in November. The size depends on how effectively each party can use wedge issues to drive them to the polls or across the aisle, the researchers said. Larry J. Sabato, director of the Center for Politics at the University of Virginia, said the vast majority of voters today in this highly partisan era vote party line.

Wedge issues and “microtargeting” were wielded heavily in the 2004 presidential election to attract voters in the close race between Republican George W. Bush and Democrat John Kerry, according to the book “The Persuadable Voter: Wedge Issues in Presidential Campaigns.” Those hot-button issues then included stem cell research and immigration.

The Gallup Poll’s summer survey on issues showed Trump, while slightly trailing Clinton overall nationwide, held a “modest” edge in most of three of the top five issues of the economy, jobs and terrorism. Meanwhile, Clinton holds a “commanding” edge in health care and education.

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Clinton, however, attracts most voters in the lower-priority issues of foreign affairs, immigration, treatment of minorities, distribution of wealth in the United States, social issues including same-sex marriage and abortion, and climate change — all of which have in past elections become effective wedge issues.

Climate change, for example, is an “extremely or very important” issue for 47 percent of all voters and more than twice as many voters in the Gallup poll felt Clinton will better handle the issue than Trump. Trump has called climate change “a hoax” and promised to “cancel the Paris Climate Agreement” signed by 200 countries to lower carbon emissions.

Trump’s position appeals to conservatives and Midwestern swing state voters employed in the auto industry. Clinton supports the agreement and has strengthened her rhetoric in recent months. She called climate change “an urgent threat” that “requires an aggressive response,” which is a view favored by college-educated voters across party lines and liberals.

“Polls show that a vast majority of Americans support a woman’s right to choose and some modest gun controls, for example, and a small majority even support gay marriage,” said Steven Gillon, history professor at the University of Oklahoma, author of books on American politics and resident historian at The History Channel. “This presents a big problem for Republicans.”

However: “Social conservatives are more passionate, better organized, especially through local churches, than are their more liberal counterparts,” Gillon said. “So even though polls would seem to show a clear advantage for Democrats, that may not be the case. Today, Trump’s challenge is to disarm more liberal-minded suburban voters while maintaining the energy and enthusiasm of hard-core social conservatives. Clinton’s challenge is to find ways to motivate her more liberal supporters and making sure they show up at the polls.”

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“They are trying to mobilize independents in the middle,” said Professor Brooks D. Simpson of Arizona State University. “I think both parties’ bases are pretty much established. The only question is turnout.”

He said he expects Clinton will use abortion rights as a wedge issue to reach more independents and Republican women who support reproductive rights as a top issue.

“The way to take them is you emphasize an issue and force him to declare a position,” Simpson said. “If you pin Donald Trump down, he will be a pro-choice person and then a lot of his conservatives would be lost.”