Politicians warn that surging left-wing party Podemos is a "Trojan horse" disrupting the independence drive, while centre-right Ciudadanos vows to sink the secessionists.
Many in the rich industrial region, including its conservative leader Artur Mas, want to create a new state in Europe in defiance of the Spanish government. Mas got a boost when nearly two million Catalans backed independence in a symbolic poll in November.
Banned by Spanish courts from holding a full referendum, Mas later called a regional election for next September to serve as a plebiscite on independence.
But national politics have got in his way, with the rise of the two upstart political parties, on top of Mas's disagreements with fellow pro-independence groups.
"In the coming months we will see the collapse of the secessionist plan," said Matias Alonso, the deputy leader of Ciudadanos.
"In the elections in September we will see a substantial change," he said.
Independence 'road map'
Mas and the Republican Left party with whom he shares power in the regional parliament have agreed a "road map" for independence by 2017 that they vow to implement if they retain a majority in September's vote.
The plan threatens to hurt Mas, however, as it was rejected by parties including the UCD, which forms part of his CiU grouping.
Overall, the pro-independence majority looks in danger.
For the first time since June 2011, the Catalan regional government's own opinion survey in February indicated a majority of Catalans saying "no" to independence -- 48 percent against 44 percent saying "yes".
The poll indicated that due to the rise of Podemos and Ciudadanos, the two Catalan governing parties between them could fall short of an absolute majority for the first time since 1980.
Polls show Podemos and Ciudadanos are drawing votes away from Spain's two big old parties, the governing conservative Popular Party and the main opposition Socialists.
Jordi Turull, spokesman for Mas's CiU coalition in the Catalan parliament, branded Podemos a "Trojan horse" against the independence movement.
"Podemos could sidetrack the debate," he told AFP. "In that sense it is more in line with the interests of the Spanish state than with the demands of Catalonia."
Mas told the Wall Street Journal in a recent interview: "For Catalonia, the underlying problem isn't the left-right axis, but rather the relationship between Catalonia and the Spanish state."
'No' camp mobilised
Catalonia is home to 7.5 million people and accounts for a fifth of Spain's economy.
Proud of their distinct language and culture, many Catalans say they get a raw deal from the way their taxes are redistributed to the rest of Spain.
The powerful pro-independence civil groups behind a series of mass demonstrations in recent years have been quiet since the November poll, but are now gearing up again to mobilise their supporters.
Ahead of the May local council elections, they are planning a rally on April 24 in Barcelona's Sant Jordi Palace, where the 15,000 seats have already been booked out.
The anti-independence group Sociedad Civil Catalana is also canvassing.
"If the pro-independence bubble bursts but the anti-secessionists do not respond by going to vote, things will be the same as ever," said its vice-president Susana Beltran.
Secessionists can see that "the 'no' camp is mobilised like never before," said Muriel Casals, leader of the pro-independence group Omnium Cultural.
"There will start to be a debate now, and that is welcome. There will be serious and stimulating discussions."