Sunday was the day “Silent Catalonia” finally found its voice. After months of looking on as separatist forces dominated public debate, scorned the other side as fascists and claimed to have won the argument in last week’s disputed referendum, the majority of Catalans who oppose independence from Spain took back the streets of Barcelona.

“Esta es la mayoría silenciosa!” (here is the silent majority), “Enough is enough” and “Time for common sense”, they shouted. Early estimates put the number of anti-independence demonstrators at almost a million, although the Catalan police’s figure was much lower. It was as if Barcelona’s citizens had decided to hold their own spontaneous, grassroots referendum. Their verdict: an overwhelming no.

The demonstration echoed similar unionist protests in Madrid and followed marches in about 50 Spanish cities on Saturday urging the warring parties to engage in dialogue. The question now, with less than two days to go before the presumed deadline set by the Catalan president, Carles Puigdemont, for declaring an independent state, is whether his newly energised opponents have left it too late.

Many explanations are offered for why, if most Catalans do not want a break with Madrid, the separatists have come so perilously close to their goal. Puigdemont’s party and its allies have consistently failed to win majority support. In both the disrupted 1 October referendum and an earlier, non-binding vote in 2014, the percentage of voters backing independence was in the low to mid 40s.

But unionist forces are divided. The conservative People’s party led by Spain’s prime minister, Mariano Rajoy, is unpopular in Catalonia. The Socialists, the main national opposition, have suffered debilitating leadership splits. The Catalan Socialist party opposes independence but is loath to be seen as siding with Rajoy, especially if he decides to impose direct rule from Madrid.

Artur Mas, Puigdemont’s predecessor as Catalan president, tried to turn the last regional elections, in 2015, into yet another plebiscite on independence. Despite record high turnout of 75%, a coalition of separatist parties failed to win an overall majority in the Catalan assembly. In the horse-trading that ensued, Puigdemont, Girona’s shaggy-haired answer to Boris Johnson, replaced Mas.

The outcome was hardly a ringing endorsement of independence. But the separatists’ leadership interpreted it otherwise. Egged on by partisan media, playing on Rajoy’s unpopularity at the head of a minority government in Madrid, and encouraged by opposition divisions, activists began an uncompromising push for independence leading to this month’s vote.

Showing the determination of the true believer, Puigdemont ignored a constitutional court ruling that the referendum was illegal. Rajoy’s pleas and threats were ignored too. Barcelona residents say an atmosphere of intimidation took hold in the run-up to the vote, with activists accusing those who disagreed with them of harbouring fascist sympathies.

Now that the “silent majority” has finally taken to the field, Puigdemont faces a real dilemma. If he goes ahead with a declaration of independence this week, his first and biggest problem may not be Rajoy, the Guardia Civil and direct rule from Madrid, it may be many of his Catalan constituents demanding his head.

At the same time, Rajoy should not make the mistake of interpreting Sunday’s demonstration as support for his inflexible, maximalist stance. His best course, as advocated by Inés Arrimadas of the Ciudadanos party in Catalonia, may be to use his constitutional powers to insist on fresh regional elections. New polls might lead to Puigdemont being replaced by a more accommodating figure in the separatist camp, such as Santi Vila, the business minister.

Given the current mood in Barcelona, fresh elections could result in the pro-independence coalition losing control of the Catalan assembly. Such an outcome would represent a very noisy victory for Silent Catalonia. Even that would not be the end of it, however.

The appeal of independence struggles is timeless and visceral. “Whatever we do, it has to be sold as a victory for both sides,” said Ana, a Barcelona native – or else there is the risk that confrontation will be unceasing.