WASHINGTON (Reuters) - The race for the White House remained in essentially a dead heat ahead of Tuesday's election but U.S. President Barack Obama holds a slim edge over Republican candidate Mitt Romney in the key state of Ohio, according to a Reuters/Ipsos daily tracking poll released on Sunday.
Nationally, of 3,805 polled likely voters, 48 percent said they would vote for Democrat Obama, while 47 percent sided with Romney, a former Massachusetts governor, the poll showed.
The results were similarly close in several swing states seen as determining the winner - Virginia, Colorado and Florida.
But in Ohio - perhaps the single most crucial swing state and where 18 electoral votes are at stake - Obama had 48 percent compared to Romney's 44 percent. On Saturday, Obama was ahead in Ohio by a point in the same poll.
"It's really a game of inches. It's extremely close, but things look pretty optimistic for Obama, I would say, if you do the electoral math," said Ipsos pollster Julia Clark.
"Looking over the last few days, Ohio does seem to be more comfortably on the Obama side."
All of the Reuters/Ipsos poll results on Sunday fall within the polls' credibility intervals, a tool used to account for statistical variation in Internet-based polling.
Obama and Romney have been in a neck-and-neck race for weeks. Over the weekend, both were making final appearances in a few crucial states, hoping to sway a shrinking number of undecided voters and to encourage their supporters to vote.
In Sunday's poll, they were tied in Colorado, which has nine electoral votes, and in Florida, which has 29, at 48 percent and 46 percent respectively, the online poll showed.
In Virginia, which has 13 electoral votes, Obama held on to a slim lead of 47 percent to Romney's 46 percent among likely voters.
"The popular vote is going to be really on a hair, extremely close, but I think the electoral college makes it more likely for Obama to be re-elected," Clark said.
A victory in U.S. presidential elections relies not on a popular vote count but reaching 270 electoral college votes, which are given to each state based on population size.
Nationally, the poll's credibility interval was plus or minus 3.4 percentage points for likely voters.