Here are 2012's top 10 stories, in order:

1. MASS SHOOTINGS: Armed with a high-powered rifle, 20-year-old Adam Lanza forced his way into Sandy Hook Elementary School in Newtown, Conn., and shot dead 20 children all ages 6 and 7 and six staff members in the second-worst school massacre in U.S. history. Sadly, it was only one of several mass shootings, including the killing of 12 people at a movie theater in Aurora, Colo. After the Newtown tragedy, President Barack Obama and many others, including some staunch gun-rights supporters, said it was time to find ways to rein in gun violence.

2. US ELECTION: Mitt Romney outcampaigned an eclectic field of Republican rivals, and bested Obama in their opening head-to-head debate. But on Election Day, thanks in part to a vigorous get-out-the-vote operation, Obama won a second term with a large lead in electoral votes and a solid advantage in popular votes. The GOP hung on to its majority in the House, but lost two seats to remain a minority in the Senate despite early-campaign projections of gains there.

3. SUPERSTORM: As a prelude, the storm named Sandy killed more than 70 people in the Caribbean. Then its high winds and high waters slammed into more than 800 miles of the eastern U.S. seaboard, killing at least 125 more people, and causing damage calculated at well over $60 billion the second-costliest storm in U.S. history after 2005's Hurricane Katrina. New York and New Jersey were the worst hit, with several hundred thousand homes and businesses damaged or destroyed.

4. OBAMACARE: By a 5-4 margin, the Supreme Court upheld the core elements of Obama's much-debated health care overhaul, which even he embraced as "Obamacare." To widespread surprise, the decisive vote came from John Roberts, the generally conservative-leaning chief justice appointed by Republican George W. Bush. Romney, as GOP presidential nominee, vowed to repeal the law if he won, but Obama's victory ensured the plan would proceed, with complex ramifications for insurers, employers, health-care providers and state governments.

5. LIBYA: Even amid yearlong turmoil in Libya, it was a jarring incident a Sept. 11 assault in Benghazi, widely blamed on a group with suspected links to al-Qaida, that killed U.S. Ambassador Chris Stephens and three other Americans. The U.S. ambassador to the United Nations, Susan Rice, later bowed out of consideration to be the next secretary of state because of her assertions in TV interviews that a spontaneous demonstration over an anti-Muslim video triggered the attack.

6. PENN STATE: It was a daunting year for Penn State and its storied football program. In January, longtime coach Joe Paterno died, his legacy tarnished by the sex-abuse scandal involving his former assistant, Jerry Sandusky. In June, after a wrenching trial, Sandusky was convicted of sexually abusing 10 boys, and was later sentenced to 30 to 60 years in prison. In July, the NCAA imposed severe sanctions, including $60 million in fines, a four-year postseason ban on football and a reduction in football scholarships.

7. US ECONOMY: By many measures, the economy was on a welcome upswing. The unemployment rate dipped to a four-year-low of 7.7 percent, stock markets rose, builders broke ground on more homes, and November was the best sales month in nearly five years for U.S. automakers. But overshadowing the good news was deep anxiety about the economic consequences if Obama and the Democrats failed to reach a tax-and-spending deal with the Republicans.

8. FISCAL CLIFF: Obama and Republican House Speaker John Boehner engaged in high-stakes negotiations over a deal to avert the so-called "fiscal cliff" that would trigger automatic tax hikes and spending cuts. The leaders narrowed some differences on Social Security and tax rates for the wealthy, but faced intense pressure from their bases to resist certain compromises.

9. GAY MARRIAGE: For supporters of same-sex marriage, it was a year of milestones. Obama, after a drawn-out process of "evolving," said in May he supported the right of gay couples to wed. On Election Day, Maine, Maryland and Washington became the first states to legalize gay marriage via popular vote. And on Dec. 7 the Supreme Court agreed to hear two cases that could further expand same-sex marriage rights.

10. SYRIA: What began in 2011 as an outbreak of peaceful protests escalated into full-scale civil war pitting the beleaguered regime of Bashar Assad against a disparate but increasingly potent rebel opposition. The overall death toll climbed past 40,000, as the rebels made inroads toward Assad's bastion of Damascus. The U.S. and many other nations were supporting the opposition, albeit wary of outcomes that might help Islamic extremists gain power in the region.

OTHER STORIES: Falling just short of the Top 10 was the resignation of David Petraeus as CIA director because of an affair he conducted with his biographer, Paula Broadwell.

The choices of the news professionals voting in the AP poll mirrored the news stories most closely followed by the public during the year, according to the Pew Research Center's News Interest Index. The index ranked Obama's re-election as the most intently followed story, with the Newtown shooting second and Superstorm Sandy third.

Several voters in the AP poll added a comment with their ballot, including Carol Hanner, managing editor of the Winston-Salem Journal in North Carolina.

"I believe climate change is being chronically underestimated by the media and by citizens," she wrote.

The AP, like many other news organizations, traditionally releases its year-end polls and rankings before the actual end of the year. In the case of 2004's top story poll, that meant the final list did not include the cataclysmic Indian Ocean tsunami that occurred on Dec. 26.

In 2009, AP's sports department amended its top-stories ballot part way through the voting to account for revelations about golfer Tiger Woods' marital infidelities. That ended out finishing fifth, far behind the top-ranked entry about Major League Baseball's steroid scandal.