WASHINGTON (AP) — President Barack Obama — with the help of a slowly improving U.S. economy — is gaining ground in many of the 14 states where the presidential contest with Republican Mitt Romney hangs in the balance.

Recent polls have shown Obama gaining an edge over Romney in several so-called swing states. Voters in those states do not reliably support the candidate of either the Republican or Democratic party.

Their importance derives not only from their unpredictability but also from the U.S. presidential election process, which depends on the electoral college and not the popular vote.

In 2000, for example, Democrat and former Vice President Al Gore won the most popular votes nationwide, but former President George W. Bush won the presidency because he rolled up more electoral college votes.

That race finally was decided by the U.S. Supreme Court in a hugely controversial ruling that votes in Florida, which initially showed Bush as winner, would not be recounted statewide.

That gave Bush all of Florida’s 27 electors and the presidency.

The electoral college is a product of the earliest years of American history and was put in place to protect the interests of small-population states.

It was a compromise among the founding fathers, who wrote the U.S. Constitution. Some wanted the president chosen by Congress, others wanted the popular vote to determine the election.

Under the compromise, the electoral college grants the presidential candidate who wins the popular vote in each state the number of electors allocated to that state.

Each state has one elector for each member of the House of Representatives. The number of House members is allocated according to population, with the smallest-population states having only one representative.

But each state, regardless of population, has two senators and, therefore, two electors in the college. Thus, small-population states are granted fewer electors but have proportional power according to population.

There currently are 438 members of the House and 100 Senators, a total of 538 electors. The winning presidential candidate must accumulate 270 electors — half plus one — to win the White House.

The presidential election, thus, amounts to 51 — the number of U.S. states plus Washington, D.C. — individual winner-take-all elections.

The swing states are Arizona, Colorado, Florida, Iowa, Michigan, Minnesota, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin. Current polling shows Obama leading in eight, Romney in three and three with new polling unavailable.

The unemployment rate, a key measure of economic recovery, has dropped more sharply in several swing states than in the nation as a whole. A resurgence in manufacturing is helping the economy — and Obama’s chances — in the industrial Midwestern states of Ohio and Michigan.

And Arizona, Nevada and Florida, where unemployment remains high, are getting some relief from an uptick in tourism.

The Great Recession of 2007-2009 hit several swing states particularly hard. Unemployment peaked at 14.2 percent in Michigan, where the auto industry faced ruin.

It also hit double digits in Arizona, Nevada and Florida, which were at the center of the housing bust, and in North Carolina, which lost jobs in textile and furniture plants.

In 2010, the economic misery helped Republicans retake control of the House and gain seats in the Senate. But the Republicans cannot count on a repeat when voters return to the polls — with much more at stake — on Nov. 6.

After an agonizingly slow recovery, several swing-state economies are finally accelerating:

— The job market is improving in Michigan and Ohio. In Michigan, unemployment fell to 8.5 percent in March from 10.5 percent in March 2011. And in Ohio, it dropped to 7.5 percent from 8.8 percent over the same period, putting it well below the national average of 8.2 percent. A Fox News poll released Friday showed Obama leading Romney 45 percent to 39 percent among registered voters in Ohio.

Many blue-collar workers in Ohio and Michigan credit the federal bailout of General Motors and Chrysler for saving tens of thousands of auto industry jobs. Romney opposed the auto bailout.

— In Florida, unemployment tumbled to 9 percent in March from 10.7 percent a year earlier. That was more than twice the nationwide drop of 0.7 percentage point (from 8.9 percent to 8.2 percent) over the same period. A rise in tourism is helping.

— Even Nevada, a focal point of the real estate collapse, has seen some improvement: Unemployment dropped to 12 percent in March from 13.6 percent a year earlier.

— Unemployment is down over the past year in the 10 other states the Associated Press identifies as swing states: Arizona, Colorado, Iowa, Minnesota, New Hampshire, New Mexico, North Carolina, Pennsylvania, Virginia and Wisconsin.

But things can change swiftly and the economic recovery remains fragile. A month before the most recent polling, for instance, Obama was running behind or neck-and-neck with Romney in battleground states.

A jobs recovery fizzled in mid-2011, so there is no guarantee the unemployment rate will continue to fall this year.

Indeed, Romney was quick to pounce after the government said job creation plunged in March after three strong months of growth. Romney called the numbers “weak and very troubling…. Millions of Americans are paying a high price for President Obama’s economic policies.”

Higher gasoline prices, up 60 cents this year to a national average $3.88 a gallon, could also turn voters against Obama. Still, prices have dropped over the past two weeks, and analysts say they could fall further.

Copyright 2012 The Associated Press.