(Reuters) - Republican Mitt Romney has erased President Barack Obama's advantage in the race for the White House and the two candidates are now tied among likely voters, according to a Reuters/Ipsos tracking poll released on Tuesday.

With the November 6 election four weeks away, Romney and Obama each command 45 percent, the daily tracking poll found.

The Democrat held a steady lead in the poll for most of September, but Romney narrowed the gap following a strong debate performance last week. Obama had been leading by 2 percentage points in the last poll on Sunday.

The poll reflects a closely divided electorate and a sluggish economy, Ipsos pollster Cliff Young said.

"It's a much tighter race and Romney became much more presidential in people's eyes," Young said. "Things are probably back to where they should be."

Romney's improved prospects have shown up in other polls, after the former Massachusetts governor launched aggressive criticism of his rival's economic record during the debate in Denver.

Obama's advantage had already started to fade before the debate as Romney recovered from a series of campaign missteps.

The online survey of 1,157 likely voters was conducted between Oct. 5 and Oct. 9. The precision of Reuters/Ipsos polls is measured using a credibility interval, which in this case was plus or minus 3.3 percentage points.

Among a larger sample of 1,370 registered voters, Obama led by 3 percentage points, 45 percent to 42 percent.