UPDATE / 4.30pm: A snap poll by CNN has US President Barack Obama winning the third presidential campaign debate, which focused on foreign policy, 48% to 40%. CNN did not give a sample size.
Democratic polling firm Public Policy Polling (PPP) questioned 500 swing voters in 11 states. It found Obama won the debate by a margin of 53% to 42%, with 5% undecided.
A CBS sample of 500 uncommitted voters found Obama won 53% to 23%, with 24% calling it a tie.
The broadcaster described the result as "a flip of the first debate", which the uncommitted group gave to Mr Romney. The second debate was tied.
Respondents to the CBS poll thought Mr Obama sounded stronger on foreign policy in tonight's debate by 64% to 36%.
The sample was split 50% to 50% on who would do a better job handling China.
Mr Obama, listless in the first debate but more front-foot in the second, again took a more aggressive approach.
Polls achingly close ahead of third and final presidential debate today
Going into the third and final presidential debate (2pm today NZ time), the race is achingly close.
Various daily tracking polls have the race tied, or Obama or Romney a nose ahead.
The consensus, however, is that Republican challenger's poll bounce after the first debate faded after Obama's comeback performance in the second encounter.
An NBC-Wall Street Journal poll released over the weekend has the face a dead heat at 47% each.
Electoral College maths favours Obama
A number of other polls have Romney slightly ahead for a 0.8% lead in one poll-of-polls.
But uder US presidential voting system - which allocates Electoral College votes to states based on population - Obama could win the presidency without winning the popular vote.
With most East and West Coast states in Obama's camp, and most of the South in Romney's, the campaigns are focusing on 16 swing states - easily the largest of which are Florida and Ohio.
After the first debate, Romney nudged ahead in Florida and has clung to small lead according to most polls, but Obama has held a narrow lead in Ohio throughout (although the very latest polls show a tie).
Pundits say it will be hard for Mr Romney to gain the 270 electoral votes required to win without winning both Florida and Ohio - plus likely at least one of the other 14 battleground states.
The third debate will focus on foreign policy.