WASHINGTON (Reuters) - President Barack Obama and Republican Mitt Romney are dead even on a national level but Obama holds a slight edge in three of the most hotly contested states in Tuesday's election, according to a Reuters/Ipsos poll released on Friday.
Obama leads Romney among likely voters by a margin of 3 percentage points in Virginia and 2 percentage points in Ohio and Florida, the online tracking poll found.
None of the polls indicates a clear lead for Obama because each falls within the survey's credibility interval, a tool used to account for statistical variation in Internet-based polls.
The two candidates are tied in Colorado, the tracking poll showed.
Nationwide, they are tied at 46 percent each. Neither candidate has held a clear lead in the four-day national tracking poll since early October.
But the national poll may be less relevant at this point because Tuesday's election will be won or lost in the eight or nine states that remain truly competitive.
Collectively, the state polls indicate that Obama holds a slight advantage in the state-by-state battle to rack up the 270 electoral votes needed to control the White House.
Voters seem to share this assessment. Regardless of who they personally support, some 52 percent said they expect Obama to emerge the victor in the election, while 32 said they thought Romney would win.
Because many of the largest states are considered a shoo-in for Obama, Romney needs to win most of the nine or so states that are considered to be truly competitive in the election.
Obama holds his greatest advantage in Virginia, a state that was considered reliably Republican until the 2008 election. Obama leads Romney 48 percent to 45 percent there, just within the poll's credibility margin of 3.4 percentage points.
Romney will have a hard time winning the White House if he does not carry Ohio. Obama leads there by 47 percent to 45 percent.
Romney until recently held a narrow advantage in Florida. Now Obama leads by 48 percent to 46 percent.
In Colorado, the two candidates are tied among likely voters at 46 percent each.
Among all registered voters, Romney leads in Colorado and Obama leads in the other three states.
Early voting playing a greater role this year than in previous races, and 27 percent of those surveyed nationwide said they had already cast their ballots. Obama led Romney among this group by 51 percent to 44 percent, a statistically significant margin.
In Colorado, 60 percent of those surveyed said they had already voted. Obama led this group by 51 percent to 43 percent.
Obama led Romney by 52 percent to 45 percent among early voters in Florida, where 38 percent said they had already cast their ballots.
One-third of those surveyed in Ohio said they had already voted, and Obama led by 59 percent to 35 percent.
Early voting is playing a less prominent role in Virginia, where only 10 percent said they had already cast their ballots. Obama led Romney by 51 percent to 45 percent, a statistically insignificant margin given the small sample size.
Democratic candidates led in the three states of the four states surveyed where a Senate seat was in play.
Democrat Tim Kaine led Republican George Allen by 47 percent to 44 percent in Virginia, while in Ohio Democratic Senator Sherrod Brown led Republican Josh Mandel by 50 percent to 42 percent. In Florida, Democratic Senator Bill Nelson led Republican Connie Mack by 53 percent to 41 percent.
Editing by Alistair Bell and Vicki Allen