* Romney viewed positively for first time in campaign
* Republican nominee makes gains on economic issues
* He shores up support among Republican voters
* Obama leads Romney 48 percent to 43 percent in poll (Adds details, background)
By Andy Sullivan
WASHINGTON, Oct 4 (Reuters) - Republican presidential challenger Mitt Romney gained ground on Democratic President Barack Obama after a strong performance in their first debate heading into the Nov. 6 election, according to a Reuters/Ipsos poll taken after their prime-time face-off.
Romney is now viewed positively by 51 percent of voters, the first time he has enjoyed a net positive in the U.S. presidential race, the poll found. Obama's favorability rating remained unchanged at 56 percent, according to the poll.
Romney moved ahead of the president on several core issues after Wednesday's debate, which was widely seen as a victory for the Republican candidate.
Voters now see Romney as a better bet to boost the economy, spur job creation and manage the budget deficit, the poll found. He narrowed Obama's advantage on taxes, the Social Security retirement program and the Medicare health insurance program for the elderly and disabled.
Romney's strong performance could make the race more competitive, Ipsos pollster Cliff Young said.
"If he has more debates like this, is able to push through his message and target undecideds, we might see movement in voting intention, but he needs a lot more of this," Young said.
Obama and Romney have two more debates before the election.
The poll found that Obama's 7 percentage point advantage over Romney had narrowed to a lead of 5 percentage points, 48 percent to 43 percent.
The online poll surveyed 536 registered voters on Wednesday and Thursday after the debate. It has a credibility interval of 4.8 percentage points.
A truly accurate reading on the debate's impact on the race will not be possible for several days, Young said. That is because the poll drew on a smaller pool of voters, taken over a shorter period of time, than the Reuters/Ipsos daily tracking poll that measures the prospects of each candidate.
Romney has trailed Obama in opinion polls since early September and had faced rising criticism from within his own party after a series of campaign missteps.
A secretly recorded video released last month showed Romney at a private fundraiser denigrating 47 percent of Americans as government-dependent victims who pay no taxes and would back Obama "no matter what." That followed Romney's widely criticized response to attacks on U.S. compounds in Libya and Egypt.
Romney needed a strong debate performance to change the dynamics of the race. The poll suggested he may have done so.
Twenty-seven percent of those surveyed said the debate had prompted them to see Romney in a more positive light, while 19 percent said it caused them to view him more negatively and 40 percent said it did not change their opinion.
Obama did not appear to suffer any damage. Fifty-four percent said the debate did not change their opinion of the president, while 16 percent said their opinion had improved and 18 percent said they viewed him more negatively.
Obama's favorability ratings remained unchanged, as 56 percent said they viewed him favorably and 44 percent said they viewed him unfavorably. His standing improved among independents by 8 percentage points.
Romney appears to have made his greatest strides among his fellow Republicans - a development that could help his fundraising and get-out-the vote efforts in the final weeks of the campaign.
Forty-six percent of Republicans said their opinion of Romney was "very favorable" after the debate, a gain of 10 percentage points.
(Reporting by Andy Sullivan; Editing by Will Dunham)