WASHINGTON — President Barack Obama is in a better position to win November’s election than any presidential candidate since Bill Clinton in 1996, according to a nationwide poll released Wednesday that shows him with an eight-percentage- point lead among likely voters.

In the survey by the Pew Research Center, Obama is ahead of Republican presidential nominee Mitt Romney 51 percent to 43 percent, the largest advantage in September the survey has shown for any presidential nominee among likely voters since 1996, when Clinton — then seeking re-election — led Republican challenger Bob Dole, 50 percent to 38 percent.

At the same point in 2008, Obama and Arizona Sen. John McCain, the Republican, were tied in the Pew poll at 46 percent. Obama went on to win the White House, getting 53 percent of the vote to McCain’s 46 percent.

“It’s a substantial lead for Obama” in the latest poll, said Carroll Doherty, associate director of the Washington-based Pew Research Center. “His image is stronger at this point and he’s doing better on most, but not all, issues.”

The survey was taken Sept. 12-16, after both national party conventions and before a videotape surfaced of Romney referring to 47 percent of Americans as government-dependent “victims” who will support Obama in the election.

A poll of likely voters taken during the same period by NBC News and the Wall Street Journal gave Obama a five-point lead among likely voters, 50 percent to 45 percent. Still, the Gallup tracking poll covering the Sept. 12-18 period showed Obama with a one-point lead, 47 percent to 46 percent. That is down from a seven-point lead, 50 percent to 43 percent, Obama had in the tracking poll during the period Sept. 5-11.

A Sept. 11-17 USA Today/Gallup poll of registered voters in the swing states of Colorado, Florida, Iowa, Michigan, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia, and Wisconsin, put Obama ahead by two points, 48 percent to 46 percent.

A USA Today/Gallup survey of 885 registered voters taken Tuesday found 36 percent saying they were less likely to vote for Romney as a result of his videotaped comments, with 20 percent saying they were more likely to back him and 43 percent saying that his remarks wouldn’t make a difference. The margin of error was plus or minus 4 percentage points.

In the Pew poll, Obama had a 56 percent to 38 percent advantage among likely women voters. Romney led among men, 48 percent to 46 percent.

Among registered voters, almost two-thirds, 66 percent, said Obama connected well with ordinary Americans, compared with 23 percent who said the same thing about Romney.

The poll found registered voters saying Obama would do a better job than Romney on health care, 52 percent to 39 percent, and on Medicare, 51 percent to 38 percent.

Romney’s running mate, House Budget Committee Chairman Paul Ryan, sponsored legislation passed by House Republicans to end traditional Medicare and offer vouchers for private insurance or a government plan with a cap on expenditures for when those Americans now under age 55 become eligible for the program. The legislation, blocked in the Senate, also repealed Obama’s health-care law, which extends coverage to 30 million uninsured Americans and is modeled after similar legislation Romney enacted as governor of Massachusetts.

In the Pew poll, Obama was favored, by 53 percent to 38 percent, as the candidate who would make wise decisions on foreign policy; by 48 percent to 42 percent as the one who would do a better job of dealing with taxes; and by 46 percent to 45 percent as best able to improve the job situation. Romney led, 46 percent to 43 percent, on the question of who would do a better job of reducing the deficit.

The survey of 2,192 likely voters had a margin of error of plus or minus 2.4 percentage points. Thirty-seven percent of those surveyed said they were Democrats, 30 percent Republicans and 30 percent independents. In the 2008 exit polls of voters, 39 percent were Democrats and 32 percent identified as Republicans. The poll’s survey of 2,424 registered voters had a margin of error of plus or minus 2.3 percentage points.

A CBS News/New York Times/Quinnipiac University survey released today of three battleground states shows Obama with a 50 percent to 46 percent edge in Virginia and a 51 percent to 45 percent lead in Wisconsin, Ryan’s home state.

Obama led Romney in Virginia, 49 percent to 45 percent, and in Wisconsin, 49 percent to 47 percent, in August surveys.

The latest poll shows a virtual tie in Colorado — Obama with 48 percent and Romney with 47 percent. Romney led in last month’s poll, 50 percent to 45 percent.

“All the bounces seem to be over as the candidates buckle down for a seven-week down-to-the-wire race to the finish,” said Peter Brown, assistant director of the Quinnipiac polling institute in Hamden, Conn. While Romney has lost ground, “the races are close,” Brown said.

“President Obama has an edge over Governor Romney on who can best handle a variety of issues — health care, Medicare, national security and women’s reproductive rights,” Brown said. “But on the number one issue to voters, the economy, the two are pretty much tied in the three states. On the topical question, given events in the Middle East, of who can best handle an international crisis, the president enjoys double- digit leads.”

Among women, Obama led 52 percent to 43 percent in Colorado; 54 percent to 42 percent in Virginia; and 55 percent to 42 percent in Wisconsin.

Romney was ahead 52 percent to 43 percent among men in Colorado; 51 percent to 45 percent in Virginia; and 49 percent to 47 percent in Wisconsin.

In Colorado, Obama led among independent voters, 47 percent to 46 percent, while Romney led in Virginia, 53 percent to 42 percent, and in Wisconsin, 50 percent to 44 percent.

The survey was taken Sept. 11-17 of 1,497 likely voters in Colorado with a margin of error of plus or minus 2.5 percentage points, 1,474 likely voters in Virginia with a margin of error of plus or minus 2.6 percentage points, and 1,485 likely voters in Wisconsin with a margin of error of plus or minus 2.5 percentage points.