BARCELONA, Spain — Catalonia’s silent supporters of Spanish unity found their voice on Sunday, thronging into the center of Barcelona as part of a huge rally that reverberated with chants in support of a united Spanish state and against agitators for independence.

They demonstrated solidarity with the vilified national police and proudly waved a red-and-yellow national flag that for decades had carried the stigma of a taboo nationalism.

“Catalonia is not all for independence,” said José Manuel Alaminos, a 64-year-old lawyer. He said that Carles Puigdemont, the regional president who has led the independence movement, “is supposed to represent all of us.”

The separatist push has brought about one of Spain’s worst constitutional crises since the end of the Franco dictatorship nearly 43 years ago.