Updated

WASHINGTON -- Former Massachusetts Gov. Mitt Romney has surged to a clear lead in the Republican race for the presidential nomination, but his party's attacks on President Obama's economic stewardship have yet to shake the president's lead over the GOP, according to a Wall Street Journal/NBC News poll released Wednesday.

At the same time, rising anxieties over the economy continue to erode the political environment for the president, pointing to a tight re-election fight.

"The president has substantial advantages but is still in for a very difficult race," said Bill McInturff, a Republican pollster who co-directs the Journal/NBC News poll with Democrat Peter Hart.

The poll of 1,000 adults, conducted between June 9 and 13, put Obama's approval rating at 49 percent, where it was in April, before Usama bin Laden's killing had helped nudge it up to 52 percent in May. Forty-six percent said they disapproved of the job Obama is doing, a five-point jump from May.

Of those who said they were likely to vote in the Republican primaries next year, 30 percent said they back Romney, up from 21 percent last month, when former Arkansas Gov. Mike Huckabee and businessman Donald Trump were still possible contenders.

Former Alaska Gov. Sarah Palin, who has yet to say whether she is running, now comes in a distant second, with 14 percent support. Other leading hopefuls, such as former Gov. Tim Pawlenty and Rep. Michele Bachmann, both of Minnesota, are in single digits.

When the field was narrowed to six names, Romney's support surged to 43 percent, with Reps. Bachmann and Ron Paul of Texas at 11 percent, former Sen. Rick Santorum of Pennsylvania at 9 percent, former House Speaker Newt Gingrich at 8 percent and Pawlenty at 7 percent.

Concerted Republican attacks on Obama have so far failed to fundamentally change public opinion about him. The president still leads GOP White House contenders including Mr. Romney, and 62 percent said the nation's economic malaise is one the president inherited, not one he caused.

"There's nothing to suggest the public's really turned on him," Hart said.

Still, a year and a half before Election Day, the political environment has grown more perilous for the president as economic gloom remains high. Some 62 percent of respondents said the U.S. is on the wrong track, up 12 percentage points from a month ago. Forty-four percent said the U.S. is heading for another recession, a slightly larger share than those who don't foresee a "double dip."