ST PAUL, September 3, 2008 (AFP) - Democrat Barack Obama is pulling ahead of his Republican rival John McCain in two key swing states of Iowa and Minnesota, but remains in a dead heat in Ohio, a new poll said Wednesday.

The biggest margin was in Iowa, where 55 percent of the 912 people polled said they would be more likely to vote for Obama compared with 40 percent for McCain, in the CNN-Time poll carried out from Saturday to Tuesday.

'Obama is winning in all regions of the state -- even in the western counties where (President) George W. Bush beat (Democrat) John Kerry by 17 points,' said CNN Polling Director Keating Holland, referring to the 2004 presidential elections.

'Obama is winning rural voters in Iowa -- not something you see in many other states.'

Iowa handed Obama his first victory in the Democratic primary race when he beat former first lady Hillary Clinton in the very first nominating contest in January.

In Minnesota, where 807 people were questioned, Obama came on top with 53 percent of support compared with 41 percent for the Republicans.

The closest race was seen in Ohio, which could prove key to either party's bid to capture the White House in the November 4 presidential election.

Illinois senator Obama was narrowly ahead with 47 percent of the vote among some 776 voters polled, with McCain on 45 percent.

'In Iowa and Minnesota, white voters are backing Obama. In Ohio, white voters are supporting McCain. What about those blue-collar white voters that were so important for Clinton in Ohio? They're pretty solidly for McCain,' said CNN political analyst Bill Schneider.

The margin of error in all the polls, taken just after the end of the Democratic nominating convention in Denver and before the Republican jamboree really got underway this week was 3.5 percentage points.

However, a second poll showed that independent candidates standing in the three states could siphon votes away from both Obama and McCain.

Voters were also asked how they would vote if Green Party candidate Cynthia McKinney, Libertarian Party candidate Bob Barr or independent consumer rights champion Ralph Nader were standing in their state.

In Ohio the race narrowed even further, with the level of support for Obama dropping two points to 45 percent of the voters, compared to 44 percent for the Arizona senator McCain.

In both Iowa and Minnesota, Obama stood at 51 percent with 37 percent for McCain in Minnesota and 38 percent in Iowa.