INDIANAPOLIS -- A poll released on Tuesday showed Sen. Barack Obama with a slight lead in Indiana over Sen. John McCain, 48 to 46.

The poll conducted by Public Policy Polling suggested that Obama's lead in the state is being fueled largely by concern over the economy, with 60 percent of respondents ranking the issue as their biggest concern when deciding whom to vote for in November.

"Barack Obama has a real chance to pull off a Midwestern sweep," said Dean Debnam, president of Public Policy Polling, in a press release. "Indiana and Missouri are the two toughest wins for him there but we've found him with a two point lead in each of those states over the last week. If Obama can hold on to enough white voters in those places his overwhelming black support will put him over the top."

Obama leads with black voters 89 to 11, with McCain leading with white voters 51 to 42, the poll showed.

Still, Obama's success isn't helping Democratic gubernatorial candidate Jill Long Thompson, the poll contents. It shows Gov. Mitch Daniels leading his opponent 57 to 36.

Thompson's campaign on Tuesday began running a new television ad, her first in seven weeks.

Obama will make another visit to Indianapolis on Thursday, campaign officials said.