Romney would repeal Obama's health care law but hasn't spelled out what he'd do instead. On Medicare, he favors the option of a government payment to help future retirees get private coverage.
The risk of expanding coverage: Health costs consume a growing share of the stressed economy. The risk of not: Millions continue uninsured or saddled with heavy coverage costs as the population grows older.
An estimated 11.5 million illegal immigrants are living and often working in the United States. Figuring out what to do with them has confounded Washington for years.
Lax enforcement could mean more illegal immigrants competing with citizens and legal immigrants for jobs and some social services. A too-tight policy could mean farmers and others in industries that rely on the cheaper labor of illegal immigrants are left begging for workers, passing higher costs on to everyone else or going out of business.
Obama backed the DREAM Act, a failed bill that would have provided a path to legal status for many young illegal immigrants. In June, Obama decided to allow as many as 1.7 million of them to stay for up to two years. Romney has said he would veto the DREAM Act, though during the second presidential debate he said he supports a path to legal status for young illegal immigrants. He would honor any work permits issued under Obama's plan to delay deportations for many young illegal immigrants but wouldn't accept new applications for the programs.
The income gap between the rich and everyone else is getting larger, while middle incomes stagnate. That's raised concerns that the middle class isn't sharing in economic growth as it used to.
Obama would raise taxes on households earning more than $250,000 a year, plus set a minimum tax rate of 30 percent for those earning $1 million or more. He also wants to spend more on education, "a gateway to the middle class." Romney would cut taxes more broadly and says that will generate enough growth to raise all incomes.
Income inequality has risen for three decades and worsened since the recession ended. The Census Bureau found the highest-earning 20 percent earned 51.1 percent of all income last year. That was the biggest share on records dating to 1967. The share earned by households in the middle 20 percent fell to 14.3 percent, a record low.
Much of America's infrastructure — the interstate highway system, mass transit networks and more — is well-over half a century old and in need of serious repair and modernization. System breakdowns and bottlenecks are slowing commerce, at a cost to the economy and America's global competitiveness. The World Economic Forum put the U.S. 24th last year in the quality of its infrastructure, down from fifth in 2002.
The dilemma facing any president is how to maintain critical public works when budgets are crippled. Both candidates say infrastructure is important. The divide is over how to pay for it, and which projects.
Obama has favored stimulus-style spending and pushed for innovations like high-speed rail. Romney favors less federal involvement. He also shuns the idea that public-works spending is a good way to jumpstart the economy, saying decisions on projects should be based on need and potential returns.
With the Iraq war over and Afghanistan winding down, Iran is the most likely place for a new U.S. military conflict.
Obama says he'll prevent Iran from acquiring nuclear weapons. He hopes sanctions alongside negotiations can get Iran to halt uranium enrichment. But the strategy hasn't worked yet. Obama holds out the threat of military action as a last resort.
Romney accuses Obama of being weak on Iran. He says the U.S. needs to present a greater military threat.
Attacking Iran is no light matter, however. That is why neither candidate clearly calls for military action.