As President Obama nears a decision on the Keystone XL pipeline, a poll Tuesday finds 66% of Americans support the Canada-to-U.S. project. The numbers come amid continuing efforts to clean up a major new oil spill in Arkansas and lingering problems from the 2010 BP blowout on the Gulf Coast.

In the Pew Research Center survey, 66% of U.S. adults say they favor the pipeline, which would carry heavy crude or tar sands from Canada through the Midwest to Texas refineries, and 22% oppose it. Support is highest among Republicans (82%) and independents (70%) and lowest among Democrats (54%), according to the poll of 1,501 adults taken March 13-17.

“There’s been pretty consistent support for traditional energy sources,” says Pew’s Carroll Doherty, noting similar Keystone XL support in other recent polls by Fox News and Yale University. He says he doubts the Arkansas spill, which occurred after the Pew poll was taken, would do much to alter attitudes on Keystone. He says support for offshore oil drilling bounced back quickly after the 2010 BP oil spill, the largest in U.S. history.

Pew’s results come as environmentalists intensify their opposition to the pending northern leg of the Keystone XL, likely to get Obama’s final decision as early as this summer. Critics say the project is unnecessary and poses safety risks. They point to Friday’s ExxonMobil pipeline spill of thousands of barrels of heavy Canadian crude oil in Mayflower, Ark., that prompted the voluntary evacuation of 22 homes.

ExxonMobil’s ongoing cleanup measures can handle 10,000 barrels of spilled oil but “we don’t think it’s that many,” says company spokesman Alan Jeffers.He says the removal of oil-soaked soil, which began Tuesday, and its replacement with new sod should be finished in a few days. After that, he says it’s up to health authorities to decide when residents can return to their homes. The U.S. Environmental Protection Agency considers any spill of 250 barrels or more to be “major.”

“We don’t know what caused it (the spill) yet,” Jeffers says, adding the company has begun its own inquiry. On Tuesday, Arkansas Attorney General Dustin McDaniel said he’ll also investigate the spill’s cause and impact. Jeffers says it’s the first spill for the Illinois-to-Texas Pegasus pipeline, which was built in the late 1940s and carries conventionally drilled oil from Alberta’s Wabasca region that’s about as heavy as the tar sands.

Still, Jeffers says he doesn’t understand environmentalists’ alarms about the Keystone XL, saying it will be “a state-of-the-art, new pipeline.”

“The fact remains that pipelines are the safest way to move oil and other products to markets to meet consumer demands and maintain our quality of life,” says Shawn Howard of Alberta-based TransCanada, Keystone XL’s developer.

Howard says the pipeline has already undergone four federal environmental reviews, including a largely positive one last month from the U.S. State Department that said the project won’t make much of a difference to climate change because the tar sands will likely be developed anyway.

Still, environmentalists say the State Department is wrong, and the Arkansas spill shows how heavy crude oil can corrode a pipeline and increase its risk of rupture.

“Tar sands poses an additional risk to pipelines,” says Anthony Swift of the Natural Resources Defense Council, an environmental group. He says 38 miles of the Kalamazoo River remain contaminated because of a 2010 Enbridge pipeline spill in Michigan.

Jim Murphy of the National Wildlife Federation, a private advocacy group, says, “There’s a very heavy odor of oil in the air,” from the spill in Mayflower, a small town about 20 miles northwest of Little Rock. “We don’t need another Kalamazoo,” he says.

His group issued a report Tuesday that says wildlife remains hurt by BP’s Deepwater Horizon oil spill nearly three years ago in the Gulf of Mexico. The report says more dolphins are dying in the spill-contaminated areas than did before the disaster and the number of infant dolphins found dead this past January and February were six times as high as average rates.

“The Gulf oil disaster is not over,” says the report’s lead author, Doug Inkley, a senior NWF scientist.

Obama’s pending Keystone XL decision involves a pipeline that would stretch from the Canadian border through Montana and South Dakota to Steele City, Neb. The State Department is involved in the review process, because the project crosses a national border.

In January 2012, Obama rejected the initial 1,700-mile project, saying he needed more time for environmental review. TransCanada has since split the project into two parts and offered a revised route for the northern leg that avoids some environmentally sensitive areas in Nebraska. It received approval last year from the U.S. Army Corps of Engineers to begin construction of the 485-mile, $2.3 billion southern leg of the project from Cushing, Okla., to Texas.