SPRINGFIELD - When Abraham Lincoln warned in a Springfield speech, almost 150 years ago, that America was a "house divided," he was talking about slavery.

When Barack Obama speaks next month in the same city - possibly in the same building - he likely will talk about different kinds of political divisions. But he will undoubtedly invoke Lincoln's words as he launches his expected bid for the presidency.

Springfield's historic, political and architectural connection to Lincoln could figure prominently in Obama's formal Feb. 10 campaign announcement here. On that day - two days before Lincoln's birthday - the freshman U.S. senator from Chicago, a Democrat, is expected to become the most formidable African-American candidate ever to seek the White House.

On Tuesday, Obama announced he had filed papers to form a presidential exploratory committee. In a videotaped message posted on his official Web site, he said he will "share my plans with my friends, neighbors and fellow Americans" on Feb. 10 in "my home state of Illinois."

Obama's office has confirmed the announcement will be in Springfield, and it is widely anticipated he will formally kick off his presidential campaign that day.

His race, and the unifying theme of his campaign, make it easy to guess at how his handlers will want to position Lincoln's legacy among the words and pictures.

"I'm sure that the people who are advising (Obama) are trying to compare him to some of the qualities Lincoln possessed: intelligence, eloquence, - someone who seeks to unite rather than divide," said Illinois State Historian Tom Schwartz.

Invoking another famous Lincoln speech, his first inaugural, Schwartz predicted an appeal "to 'the better angels of our nature.' "

But Obama's decision to use Springfield as the backdrop is likely to be about more than just invoking the beloved president. Obama's staff says the setting also is meant to highlight Obama's eight years as a state legislator, which may prove crucial for a candidate whose biggest perceived problem right now is his lack of political experience.

"Springfield is a great place to demonstrate his work in bringing people together to solve problems, whether it was ethics reform, death penalty reform or working to give children and families the health care they need," Obama spokesman Bill Burton wrote in an e-mailed response last week to the question of why Springfield was chosen.

The choice is a departure from the tradition of making presidential announcements in candidates' hometowns or in politically important locales. Obama was born in Hawaii and has spent most of his legal and political career in Chicago.

Still, some say, the choice makes sense for other reasons, most of them symbolic.

"The Lincoln connection would be very helpful to him as a backdrop, and a Springfield audience will show his appeal in smaller communities," said Mike Lawrence, formerly a top aide to Republican ex-Gov. Jim Edgar, and now director of the Paul Simon Public Policy Institute at Southern Illinois University at Carbondale. "The backdrop is meant to enhance the message, and (Obama's) message has been about unifying the nation."

Obama's office won't say what specific sites in Springfield are being considered for the event, which is sure to draw hundreds of journalists, thousands of spectators and worldwide attention to the capital city of 113,500.

There are several Springfield venues that might work, visually or symbolically, each with pros and cons. Among them:

n The Old State Capitol. The limestone Greek Revival building was constructed beginning in 1837, after state legislators, including Lincoln, moved the seat of state government from Vandalia to Springfield. Lincoln delivered his "House Divided" speech in the building in 1858, warning that "this government cannot endure, permanently half slave and half free."

Pro: The structure is visually perfect for television, imposing and classically columned, yet small enough to keep within frame.

Con: The small interior, built before the era of big government, can hold only a few hundred people.

n The ("New") State Capitol Building. Completed in 1888 to house Illinois' ever-expanding government, the current Capitol - a massive Italian Renaissance Revival structure topped with a silver dome - is where the legislature currently meets. A 10-foot, 6-inch statue of a beardless, pre-presidential Lincoln stands in front of the building.

Pro: The marbled interiors are so impressive that Hollywood film crews have used it as a stand-in for the U.S. Capitol. Obama served in the building as a state legislator from 1997 through 2004, a fact he'll want to highlight, given concerns about his lack of political experience.

Con: It was built after Lincoln's death and has no connection to him, possibly complicating any rhetorical ties Obama will want to draw with the 16th president.

n Lincoln's Home. The two-story painted frame building in central Springfield has been fully restored to its 1860 appearance by the National Park Service.

Pro: There is a famous 1860 photo of a Lincoln campaign rally in front of the house in support of his first presidential bid - a photo that national media might find irresistible to juxtapose with a modern crowd there cheering for Obama.

Con: It's a federal historic site, which might lead some critics to question whether Obama should be using it to launch a political campaign.

n Lincoln's Tomb. Located in Springfield's Oak Ridge Cemetery, a 117-foot-tall granite spire tops the tomb, which contains the bodies of Lincoln, his wife, Mary, and three of his four sons.

Pro: The structure is visually stunning and emotionally powerful, and is surrounded by rolling, picturesque grounds.

Con: It's a tomb - perhaps not the best visual metaphor with which to start out what will certainly be a daunting political campaign.

Among the venues Obama won't be able to consider is one of Springfield's most impressive Lincoln-related sites: the newly opened Abraham Lincoln Presidential Library & Museum. The state-owned facility has an ironclad rule against hosting political events. "We're trying to keep this as neutral ground," said Schwartz, the state historian.

Obama's candidacy puts him on a long list of Illinois residents who have sought and, in few cases, won the presidency. Lincoln and President Ulysses S. Grant were born elsewhere but were Illinoisans at the time of their first-term elections, and President Ronald Reagan was an Illinois native.

The many presidential aspirants who were either born or resided in Illinois have included Lincoln nemesis Stephen Douglas, William Jennings Bryan, Adlai Stevenson, John Anderson, Jesse Jackson, Paul Simon - and Chicago native Hillary Clinton, currently a U.S. senator from New York.

Kevin McDermott can be reached at kevin.mcdermott@lee.net.