Romney's lead, which was within the poll's 4.5 percentage-point margin of error, was based on a national survey taken by UPI-CVoter pollsters in the days following the first presidential debate.
It is the first time Romney has had the lead since the UPI poll began this election cycle.
While Romney's lead is 3 percentage points among likely voters, his net gain since the seven days immediately before the debate is 5 percentage points, UPI said. During a poll taken a Sept. 27-Oct 3, 48 percent of likely voters said they would vote for Obama and 46 percent said they would back Romney.
Obama's approval ratings after the debate dipped from before, results indicated. The week after the debate, 48 percent of registered voters said they approved of Obama's performance presidency, down from 49 percent the week before. Those who said they disapproved held at 47 percent.
Thirty-six percent of registered voters asked said they believe Republicans are better able to tackle the country's problems, including the economic crisis, unemployment, poverty, inflation, healthcare, immigration, education and the war on terror. That figure is up from the 35 percent who expressed confidence in the GOP before the debate.
Thirty-one percent of registered voters said the Democrats would do a better job, which is unchanged.
The latest results are based on nationwide interviews with 1,428 registered voters of which 1,110 said they were likely to vote in the election. The margin of error for the total sample is 3.5 percentage points and the margin of error for the likely voter sample is 4.5 percentage points.