With four justices in their 70s, odds are good that whoever wins in November will fill at least one Supreme Court seat. The next justice could dramatically alter the direction of a court split between conservatives and liberals.

One new face could mean a sea change in how millions get health care, shape gay rights and much more.

Obama already has put his stamp on the court by selecting liberal-leaning Justices Elena Kagan and Sonia Sotomayor, 50-somethings who could serve a quarter-century or more. Romney has promised to name justices in the mold of the court's conservatives.

Since the New Deal, Supreme Court decisions have made huge differences in American lives, from rulings to uphold Social Security, minimum wage laws and other Depression-era reforms to ringing endorsements of equal rights. Big decisions on health care, gun rights and abortion have turned on 5-4 votes.

America's health care system is unsustainable. It's not one problem, but three: cost, quality and coverage.

The U.S. has world-class hospitals and doctors. But it spends far more than other advanced countries and people aren't much healthier. And in an aging society, there's no reliable system for long-term care.

Obama's expansion of coverage for the uninsured hits high gear in 2014. Obama keeps today's Medicare while trying to slow costs. He also extends Medicaid.

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.

The debate over banking rules is, at its core, a dispute about how to prevent another economic cataclysm.

The financial crisis that peaked in 2008 touched off a global economic slowdown. Four years later, the recovery remains painfully slow.

After the crisis, Congress passed a sprawling overhaul of banking rules and oversight. The law gives regulators new tools to shutter banks without resorting to emergency bailouts. It restricts risky lending and establishes a new agency to protect consumers from misleading marketing and other traps.

The new rules also boost companies' costs, according to Romney and many in the business community. Romney believes the law is prolonging the nation's economic agony by making it harder for companies to invest and grow. He has pledged to repeal it. Obama fought for and supports the law.

Education ranks second only to the economy in issues important to Americans. Yet the U.S. lags globally in educating its children. And higher education costs are leaving students saddled with debt or unable to afford college at all.

State budget cuts have meant teacher layoffs and larger class sizes. Colleges have had to make do with less. It all trickles down to the kids in the classroom.

Although Washington contributes a small fraction of education money, it influences teacher quality, accessibility and more. For example, to be freed from provisions of the No Child Left Behind law, states had to develop federally approved reforms.

Romney wants more state and local control over education. But he supports some of Obama's proposals, notably charter schools and teacher evaluations. So, look for them to be there whoever wins the White House.

Almost every U.S. taxpayer faces a significant tax increase next year, unless Congress and the White House agree on a plan to extend a huge collection of tax cuts expiring at the end of the year.

And there's a huge debate over how to overhaul the tax code to make it simpler, with lower rates balanced by fewer deductions.

Obama wants to extend Bush-era tax cuts again, but only for individuals making less than $200,000 and married couples making less than $250,000.

Romney wants to extend all those tax cuts and enact new ones, dropping all income tax rates by 20 percent. Romney says he would pay for that by eliminating or reducing tax credits, deductions and exemptions. But he won't say which ones would go.

Most lawmakers want a simpler tax code, but millions count on the mortgage interest deduction, child tax credit and more, making progress all but impossible.

This election probably will cost more than $1 billion. Big donors who help cover the tab could gain outsized influence with the election's winner. Your voice may not be heard as loudly as a result.

Recent court decisions have stripped away restrictions on how elections are financed, allowing the very rich to afford more speech than the rest. In turn, super political action committees have flourished, thanks as well to limitless contributions from the wealthy - including contributors who have business before the government.

Disclosure rules offer a glimpse into who's behind the money. But the information is often too vague to be useful. And nonprofits that run so-called issue ads don't have to reveal donors.

Obama criticized the Supreme Court for removing campaign finance restrictions. Romney supported the ruling. Both are using the lax rules with gusto.

The stakes now are similar to what caused the U.S. to invade almost 11 years ago: the threat of more al-Qaida attacks.

President Barack Obama says U.S. forces must not leave until Afghan forces can defend the country on their own. Otherwise the Taliban would regain power and al-Qaida might again launch attacks from there. Republican rival Mitt Romney appears to share that view.

What's often overlooked in the "al-Qaida returns" scenario is an answer to this question: Why, after so many years of foreign help, are the Afghans still not capable of self-defense? And when will they be?

The official answer is by the end of 2014, when the U.S. and its allies plan to end their combat role. The Afghans will be fully in charge, or so it is hoped, and the war will be over, at least for Americans.

The U.S. accuses China of flouting trade rules and undervaluing its currency to helps its exporters, hurting American competitors and jobs. But imposing tariffs could set off a trade war and drive up prices for American consumers.

Tensions now have spread to the automotive sector: The U.S. is seeking international rulings against Chinese subsidies for its auto and auto-parts exports and against Chinese duties on U.S. autos. Romney says he'll get tougher on China's trade violations. Obama has taken a variety of trade actions against China, but on the currency issue, he has opted to wait for economic forces to encourage Beijing to raise values.

Cheap Chinese goods have benefited American consumers and restrained inflation. But those imports have hurt American manufacturers. And many U.S. companies outsource production to China. One study estimated that between 2001 and 2010, 2.8 million U.S. jobs were lost or displaced to China.

The job market is brutal and the economy weak. Nearly 13 million Americans can't find work; the unemployment rate has been over 8 percent for more than 40 months. A divided Washington has done little to ease the misery.

The economy didn't take off when the recession ended in June 2009. Growth has never been slower in the three years after a downturn. The human toll is staggering. Forty percent of the jobless, 5 million people, have been out of work six months or more - a "national crisis," according to Federal Reserve Chairman Ben Bernanke. Wages aren't keeping up with inflation.

Obama wants to create jobs by keeping taxes low for everybody but the wealthiest, and with public-works spending, clean energy projects and targeted tax breaks to businesses. Romney proposes further cuts in tax rates for all income levels; he'd also slash corporate rates, reduce regulations and encourage oil production.

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.

Republican Romney accuses Democrat 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.

Tehran can disrupt global fuel supplies, hit U.S. allies in the Gulf or support proxies such as Hezbollah in acts of terrorism. It could also draw the U.S. into an unwanted new war in the Muslim world.