President Barack Obama holds a narrow advantage over presumptive Republican nominee Mitt Romney in three of the most pivotal presidential battleground states — Florida, Ohio and Virginia — according to new NBC-Marist polls. But, in each of these states, Obama's share of the vote is below the 50-percent threshold usually considered safe haven for an incumbent president, and Romney has narrowed the margin in these three battlegrounds since earlier this year.

In Florida and Virginia, Obama leads Romney by an identical four-point margin, 48-percent to 44-percent, among registered voters, including those who are undecided but leaning toward a particular candidate. In Ohio, Obama is ahead by six points, 48 percent to 42 percent.