Twelve-year-old twins living in Gracie Mansion. Town hall meetings in the Bronx or Queens, late into the evening. Unannounced visits at city agencies and a spontaneous game of Ping-Pong or dominoes if invited by a constituent.  If William C. Thompson Jr. is elected Tuesday, he promises to usher in a significantly different style, replacing the buttoned-down corporate efficiency of Michael R. Bloomberg with a more homespun and improvisational feel and diverse look.  If, however, Mr. Bloomberg is returned to office, he is promising a few changes, too. He is vowing to replace a third of his 40 commissioners and to demand that those who stick around come up with bold ideas. There are still a few days before the election on Tuesday, and two months before the official start of a new term. But it is already clear how unlike a Bloomberg administration a Thompson administration would be.  If Mr. Bloomberg is widely perceived as an aloof manager driven by data and unafraid to test out big initiatives before national and international audiences, Mr. Thompson is regarded as likely to make New York seem more intimate or even parochial.  A Mayor Thompson would be likely to focus on quality of life concerns, like water rates or parking tickets. Major decisions on schools, housing and other issues would probably be an exercise in consensus, with more participation by advocates and citizens.  “This administration currently administers on facts, figures and empirical data, things having to add up,” said Assemblyman Keith L. T. Wright, a Democrat from Harlem who has known Mr. Thompson since their undergraduate days at Tufts University. “I think a Thompson administration would be acting somewhat more emotionally, and be customer-friendly, people-friendly.”  Mr. Thompson, ever gregarious, is likely to interact with city employees at all levels. “It’s not going to be command and control from a centralized, on-high place,” said Gayle M. Horwitz, Mr. Thompson’s top deputy in the comptroller’s office. “Bill will be known for being very hands-on, and he will come in and sit in your office, and check on things. It’s management by walking around.”  Mr. Thompson has promised to replace all of Mr. Bloomberg’s commissioners. His most important personnel decisions would be selecting successors to Police Commissioner Raymond W. Kelly and Schools Chancellor Joel I. Klein.  For the police, the most obvious person is a former commissioner, William J. Bratton, who recently moved back to New York from Los Angeles, Mr. Thompson’s advisers said. Other possibilities include former Bratton disciples (John F. Timoney, the Miami police chief, and Garry F. McCarthy, the Newark police chief) and current police officials (Joseph J. Esposito, the chief of department, and Phil T. Pulaski, chief of detectives.)  For the schools, possibilities include a former chancellor, Rudy Crew; Kathleen M. Cashin, a widely respected superintendent in Queens; Harvey Robins, a former deputy schools chancellor under Mayor David N. Dinkins; and perhaps Joseph P. Viteritti, chairman of the urban affairs and planning department at Hunter College.  Mr. Thompson, who would be the city’s second black mayor, is likely to pick top staff members, commissioners and judges who are more diverse than Mr. Bloomberg’s. But Mr. Thompson would need to do some fund-raising for any re-election bid, and might reach out to union officials and Democratic leaders like Assemblyman Vito J. Lopez of Brooklyn, Representative Joseph Crowley of Queens and Bill Lynch, a powerful Harlem lobbyist.  “If Bill gets elected, it will all be about the Democratic establishment taking back power,” said one Democratic consultant who is not involved in the mayoral race.  Unlike other mayors, Mr. Bloomberg decided to forgo living at Gracie Mansion and guards his privacy zealously. He remained at his Upper East Side house and spends many weekends in Bermuda or at his other homes in Florida and Westchester County.  Mr. Thompson, who has spent most of his career in government, would move into the mansion with his wife, Elsie McCabe Thompson, the executive director of the Museum for African Art, and his 12-year-old twin stepchildren. That means New Yorkers would be much more likely to see Mr. Thompson than Mr. Bloomberg at, say, the latest Harry Potter movie.  New Yorkers should not, however, set their watches to Mr. Thompson’s schedule. He has a loose, undisciplined style, and is chronically late. He is also very game when citizens beseech him to participate in their activities. During one campaign stop last month at Orchard Beach, Mr. Thompson played a game of dominoes on the Boardwalk before shaking some maracas with a group of picnickers.  Though he may bring in new people, Mr. Bloomberg does not plan to behave or govern much differently than he has over the past eight years. After all, he has said, in a shoulder-shrugging way, “I am 67 years old. I am who I am.”  Mr. Bloomberg is keenly aware of the pitfalls of a third-term mayoralty, but is not reading any extra books or speaking to government veterans in preparation.  Most of the intrigue centers on whether any of his top aides  Deputy Mayors Patricia E. Harris, Kevin Sheekey and Edward Skyler, all of whom opposed the term limits extension  leave. Mr. Sheekey, Mr. Bloomberg’s political guru, is perceived as the most likely to depart.  Mr. Kelly and Mr. Klein are untouchable, according to administration officials. So are Amanda Burden, the director of city planning, and Janette Sadik-Khan, the transportation commissioner. But one longtime cog, Mark Page, the city’s budget director, plans to retire. Mr. Bloomberg does not like to fire people, according to friends and advisers. So he may rotate his commissioners to different departments to keep things fresh, in much the way he did at his company.  Mr. Bloomberg has already mapped out some priorities, and may devote more attention to transportation, community colleges and pension reform. But privately, some aides worry that Mr. Bloomberg has not yet decided what his next major initiative will be. And he will be under more scrutiny, and criticism, than in the past, given the expected election of Bill de Blasio as public advocate and John C. Liu as comptroller.  “The mayor is successful when he dominates the conversation with a big idea, even when it fails,” one administration official said. “But if it’s small stuff, that’s where he gets in trouble. And I’m not sure if we have the next big thing yet.”
The comptroller would most likely focus on quality of life and seek consensus on major issues. The incumbent has promised to shake up his current administration.