City Councilor John R. Connolly topped the ticket in a hotly contested free-for-all for four at-large seats, a race that set the stage for a new generation of Hub politicians and may signal the start of the 2013 mayor’s race, experts said yesterday.

“It’s a new chapter in a whole new book of Boston politics,” said Lawrence DiCara, a former city councilor and unofficial Hub political historian. “And the next mayor’s race begins (this) morning.”