The centre-right leader failed to win an absolute majority for his brand of what Scottish observers call "independence lite" in a general election held on Sunday.
His Convergència i Unió (CiU) alliance's share of the vote dropped despite Mr Mas's increasingly strong rhetoric calling for Catalonia, in north-east Spain, to become "Europe's next state".
He instead watched votes leak to left-wing rival Esquerra Republicana. Its vision of independence is less ambiguous and it opposes his public spending cuts.
Nationalist parties hold a majority in the parliament, and Catalan commentators said Mr Mas could do a deal with Esquerra leader Oriol Junqueras for an "independence" referendum.
But they struggled to see how the two men, with their diametrically opposed views on the economy, could govern day to day.
Mr Mas called the elections after failing to secure a fiscal pact for Catalonia, a net contributor to the rest of Spain. He did so amid an upsurge in nationalist sentiment and after 1.5 million Catalans marched for independence at a September rally.
Spanish Prime Minister Mariano Rajoy yesterday revelled in his foe's problems, saying Mr Mas's strategy "had been a fiasco".
Mr Mas's alliance colleagues were not entirely supportive. Oriol Pujol, who leads the Convergència side of the alliance, said it had left CiU "in the hands of Esquerra".
Professor Michael Keating of Aberdeen University said: "This has been a bit of a defeat for Mas.
"CiU is going to have to work with Esquerra and that is not going to be easy."
The elections were firmly about "independence". But Mr Keating cautioned against assuming the Catalans meant the same as the SNP when they used the word.
He said: "Traditionally the CiU and other parties have been pretty ambivalent about independence but their language has been hardening in recent months.
"Support for a Catalan state has jumped from about a quarter to more than a half. But I usually say that some of that support is quite soft, softer than in Scotland, where the notion of independence is now more defined."
Mas and other Catalan sovereigntists plan to hold a referendum on independence in four years, giving them time to agree what they mean by the term.
They will have to defy Mr Rajoy, who does not accept Catalonia is a "nation" with a right to self-determination. The Spanish constitution prohibits such a vote.
Rank-and-file SNP supporters were jubilant as it emerged pro-independence parties would hold a majority.
However, the party said in a statement: "The election of the Catalan government is of course a matter for the people of Catalonia. And similarly the constitutional futures of Scotland and Catalonia are rightly matters to be resolved within our respective constitutional processes."
The SNP is allied in the European Parliament with Esquerra.
Party sources have suggested their leaders were scaling down previously occasional fraternal visits to Barcelona as they try not to rock the boat with Spain, which may have the power to veto an independent Scotland's membership of the European Union.
Mr Keating said: "The SNP will be more interested in maintaining friendly relationships with the Spanish Government than with the Catalans. They won't want to be seen interfering in other countries' domestic politics."