WASHINGTON ‚?? Barack Obama publicly took the oath of office for his second term Monday in a ceremony heavily laced with references to the country‚??s long struggle toward equality for its African-American citizens. From an invocation by the widow of a slain leader of the civil rights movement that opened the formal proceedings, to the two Bibles on which Obama took the oath, one of which belonged to Abraham Lincoln and the other to the Rev. Martin Luther King Jr., the symbols of the nation‚??s 57th inaugural ceremony traced the historic arc that led toward the nation‚??s first black president. A flag-waving, cheering crowd of hundreds of thousands applauded as Vice President Joe Biden took his oath from Supreme Court Justice Sonia Sotomayor, then a few minutes later, when Chief Justice John Roberts Jr. administered the oath to the president. Four years ago, Obama took office with the country in the midst of two wars and the worst economic crisis in more than half a century. His second inauguration arrives with one war over, the other winding down and the economy recovering, but with Washington dominated by a bitter political stalemate that reflects a deep partisan divide in the nation. Obama is expected to use his inaugural speech ‚?? typically one of the most-watched events of a presidency ‚?? to address that divide, aides said. He is going to talk about the fact that our political system doesn‚??t require us to resolve all of our disputes or settle all of our differences, senior Obama political adviser David Plouffe said Sunday on CNN‚??s State of the Union. But it does impel us to act where there should be, and is, common ground. The inaugural ceremonies, themselves, highlighted the idea of bipartisanship and continuity of American democracy. Two of Obama‚??s predecessors, Democrats Bill Clinton and Jimmy Carter, were among the dignitaries gathered at the Capitol‚??s West Front. So, too, were many of the congressional Republicans who have battled Obama through the past four years. The country‚??s two living former Republican presidents, George H.W. Bush and George W. Bush, were not present; the elder Bush recently was recently released from a hospital in Houston after a bout with bronchitis. House Majority Leader Eric Cantor, R-Va., said before the ceremony that he expected most Republicans to attend the inaugural ceremony, a historic moment regardless of party. He noted that he had prime seats for Obama‚??s first inaugural and regretted not snapping any photos of the proceedings. I‚??m going to try to this time, he said. Rep. Steve King, R-Iowa, a fiery conservative, said: My thought for today is, this is a constitutional event and our forefathers would be proud we‚??re following the directions they gave us. Tomorrow we‚??ll start the political discussion. Overall, of course, the crowd, as is typical with inaugural celebrations, was heavily dominated by the president‚??s supporters, who cheered loudly as Obama‚??s motorcade arrived at the Capitol from the White House. They cheered again as the Obamas‚?? daughters, Malia and Sasha, were introduced and then, a few minutes later, for first lady Michelle Obama. In keeping with the intense enthusiasm that Obama‚??s presidency has generated among African-Americans, the audience was disproportionately black. Several spectators commented on the special significance of the swearing-in taking place on the nation‚??s Martin Luther King Jr. day observance. It‚??s particularly special that today is the MLK holiday, said David Anderson, 43, who traveled from Tampa, Fla. It‚??s kind of predestined. You can‚??t get better than that. Ed Jennings, 44, who sported a knitted Obama cap, said he anticipated the president would urge unity in his inaugural address. It‚??ll be a summary of where this country is. There was a fierce debate about where our country is going, and he won, he said. Hazel Carter, 90, of Springfield, Ohio, attended the last inauguration and wasn‚??t going to miss this one. I prayed, God, just let me keep breathing until the inauguration, she said with a laugh. The crowd isn‚??t nearly the crowd of the first time. The anticipation isn‚??t what it was, she said. It‚??s a little more subdued, but beautiful. Beautiful. I love it. Seated next to her, Thelma Lawson, 61, a nurse from Chicago, said she had not attended the swearing-in four years ago, but now I am so excited because I‚??m in the midst of what is history being made twice. Chinwe Aldridge of Fort Washington, Md., said she and her husband had not decided to come to the ceremony until Sunday night, after some prodding from their two children. I told them we could have a better shot at home on television, she said. They said they had to be here. Those are big words from little kids. At 9 a.m., the Washington region‚??s mass transit agency had counted 189,000 riders on its rail system, somewhat less than half of the record-setting crowd that jammed trains four years ago but more in line with previous second inaugurals. Obama officially took the oath of office on Sunday in a low-key ceremony at the White House, shortly before his second term officially began at noon. In keeping with a tradition of not holding the public inauguration ceremony and parade on Sundays, the president is scheduled to repeat the oath at the Capitol on Monday. Temperatures hovered in the low 30s ‚?? considerably warmer than four years ago ‚?? as spectators began gathering early in the morning. Officials were expecting about half a million spectators, down from the 1.8 million who crowded onto the Mall four years ago for the historic first swearing-in of an African-American president but comparable to the crowds for the second inaugurations of Presidents Bill Clinton and George W. Bush. Susan White, a Washington schoolteacher, her daughter Camille, 13, and her friend, Rachel, 13, said they left home at 4:30 a.m. and needed an hour to get through the elaborate security surrounding the inauguration site, but three hours later, they were still eagerly anticipating the events to come. Kerry Artis, a social services case worker from North Carolina, said she arrived at the mall at about 5 a.m., eager to see the inauguration after missing it four years ago. She said she was excited, despite the cold, because everybody‚??s here for one cause. Obama began his day along with his family and Vice President Joe Biden and his wife, Jill, with a service at St. John‚??s Episcopal Church, across Lafayette Park from the White House. After Obama delivered his inaugural address, he attended the traditional luncheon with members of Congress at the Capitol, again joined by the first lady and the Bidens. They then are to watch the inaugural parade from the reviewing stand set up outside the White House. The day is scheduled to end with the traditional inaugural balls.