Upper-income Americans may face a tax increase. Auto fuel economy standards might be raised. Stocks of construction and engineering companies could benefit.

America's decision to re-elect President Barack Obama over Mitt Romney will affect all that and other elements of the U.S. economy and financial system—from the health care law to the overhaul of financial rules.

At the same time, a gridlocked Congress will limit Obama's influence. Tuesday's election kept Republicans in control of the House. Democrats still control the Senate, but without a commanding majority.

Here's how Obama's re-election could affect key sectors:

— ECONOMY:

Obama has laid out some key themes for rejuvenating the economy: Extend Bush-era tax cuts for low- and middle-income Americans. Spend more to build and repair roads, bridges and other public structures. Provide targeted tax breaks to businesses.

Most immediately, Obama needs to persuade congressional Republicans and Democrats to reach a budget agreement to prevent the economy from falling off a "fiscal cliff." Without a deal, deep spending cuts and tax increases will start to kick in next year.

The combination of those measures could send the economy back into recession and drive the unemployment rate back up to 9 percent next year, according to estimates by the Congressional Budget Office. The rate is now 7.9 percent.

The president has pledged to cut projected deficits by $4 trillion over 10 years. He says he'd do so in part by raising the tax on investment gains. He would also raise income tax rates for individuals who earn more than $200,000 and married couples who earn more than $250,000. And a minimum 30 percent tax would be imposed on incomes above $1 million.

— STOCKS:

Stock prices plunged Wednesday in the aftermath of the election. Investors appeared rattled by the impending U.S. tax increases and spending cuts and Europe's deepening recession.

Over the long run, though, the stocks of construction and engineering companies might get a lift during Obama's second term. The president has said more spending on roads, bridges and public buildings will boost the economy. If Obama's victory helps Democrats gain seats in Congress, he'll have more support for such spending.

Other categories of stock might stumble. Financial companies had hoped to weaken rules imposed after the 2008 financial crisis. Obama's victory may ensure that the rules will remain intact. Companies will have to keep spending to make sure they comply with them.

Obama also wants to tax dividends at a higher rate. That could make financial stocks, which often pay high dividends, less appealing to investors.

Defense stocks might suffer because Obama wants to limit the growth of military spending. And some energy companies may fall because some investors think his administration will tighten pollution regulations that affect energy extraction and coal-burning power plants.

— AUTO INDUSTRY:

Obama will likely seek to further boost fuel economy standards. He's already raised the standards twice. This year, he required automakers to double their vehicles' average fuel economy to 54.5 miles a gallon by 2025.

Obama set an ambitious goal in 2011 to put 1 million electric vehicles on the road by 2015. Fewer than 30,000 electric cars have been sold in the United States this year. He wants to raise a $7,500 tax credit for electric cars to $10,000.

The president has asked the World Trade Organization to rule on Chinese subsidies for autos and auto parts and its import duties on U.S. autos. He's awaiting a decision.

— ENERGY:

The boom in U.S. oil and gas production during the president's first term will likely continue, thanks largely to new drilling techniques. But drilling could slow if the Environmental Protection Agency toughens rules governing a controversial technique called hydraulic fracturing.

Obama backs the idea of a federal clean-energy standard that would require the country to use more low-carbon energy sources, such as wind and solar for electricity and advanced biofuels and batteries in cars. 

But Republican opposition is so strong it's doubtful Obama could muster enough support in Congress for it. There would be bipartisan opposition to any administration effort to regulate emissions of carbon dioxide and other gases that scientists say contribute to climate change.

— HEALTH CARE:

Obama's victory preserves his health care overhaul, which aims to cover millions of uninsured Americans. The law requires everyone, with certain exceptions, to have health insurance or pay a penalty. It calls for the expansion of Medicaid. And it requires online exchanges where people can shop for coverage.

Health insurers that have struggled to increase enrollment in a tough economy will gain millions of new customers through the overhaul's coverage expansions. But the industry pays for that growth. Insurers will have to cover annual fees totaling $8 billion in 2014 and topping $14 billion by 2018. Those fees will go to the government to help cover the cost of expanded health care.

Among other restrictions, the law also limits how much insurers can vary pricing based on age and health.

Drug makers and money-losing hospitals may also get a boost. Hospitals typically provide charity care to uninsured people and are reimbursed for only part of it. Now, they'll be paid through insurance for more people. And drug makers will benefit from the law because starting in 2014, millions more will gain prescription coverage.

But the industry also faces new costs. Drug makers will have to give the government rebates on drugs bought through Medicaid. And they must give discounts to the elderly that will rise over time.

— FINANCIAL REGULATION:

The 2010 overhaul of financial rules marked a victory for Obama. Officials who are still carrying out the details of the law may now be more likely to take a tough stance.

One example is an oversight plan for derivatives—complex investments that speculators use to make bets and companies use to hedge against risk. Financial companies have fought for looser rules and exceptions for derivatives used by farmers who want to lock in prices before a harvest.

Obama's victory means financial companies, which mostly backed Romney, might lose influence in these negotiations. His re-election also figures to embolden the Consumer Financial Protection Bureau. The bureau aims to protect people from hidden fees and other unfair practices by financial companies.

Republicans want to give Congress authority over the bureau's budget. But without the presidency or a stronger majority in either chamber of Congress, they won't likely be able to slow the bureau's crackdown on banks, payday lenders and others.

— TECHNOLOGY:

Obama signed into law the America Invents Act to streamline the U.S. patent process. The idea was that inventors and entrepreneurs could turn their ideas into products more quickly and create inexpensive ways to resolve disputes.

Despite the law, major technology companies such as Apple, Google and Microsoft are locked in battles over the scope of their patents, particularly for smartphones and tablet computers. Tech companies and entrepreneurs say further patent reform is needed.

The president so far has resisted pressure to lower or temporarily waive corporate income taxes on the more than $1 trillion U.S. companies have piled up in overseas accounts from sales there. Many are tech companies that are keeping most of their cash offshore.

Some of the biggest hoards of foreign cash are held by Apple ($82.6 billion), Microsoft Corp. ($58 billion), Cisco ($42.5 billion) and Google ($29.1 billion). All favor a tax holiday so they could return the money to the United States without paying a huge bill to the government.

Obama hasn't ruled out a tax holiday. But he's indicated he'd consider it only as part of a broad tax overhaul.

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Contributing to this report were Associated Press writers Linda A. Johnson in Trenton, N.J., Tom Murphy in Indianapolis, Dee-Ann Durbin in Detroit, Jon Fahey and Peter Svensson in New York, Michael Liedtke in San Francisco and Daniel Wagner, Martin Crutsinger, Stephen Ohlemacher and Matthew Perrone in Washington.