A series of polls on Sunday and Monday put 'Unidos Podemos' in second place overall.
'There's no alternative to Catalan independence. You'd have to be very radical to defend what we have now,' Puigdemont says.
The country's missed deficit target may mean spending cuts or tax hikes.
The anti-austerity firebrand will forgo a deputy PM role if it blocks a progressive government.
The country's ongoing political deadlock is taking its toll.
The country just wants a new government as soon as possible
Two men were arrested last week after allegedly displaying a sign referring to Basque militant group ETA.
After a strong result in a new poll, the party's hand is strengthened ahead of coalition negotiations.
'Winter is coming' and there is no new Spanish government in sight.
A look at all the options available to PM Rajoy, the King and politicians for Spain's new government.
Four parties will likely elect the same number of MPs in the region.
However, those with long-term diseases still don't qualify for free medication, as Rajoy reverses 2012 decision.
Pablo Iglesias made the challenge at his 'alternative state of the nation' address on Wednesday.
It will be the party's first major event in the Spanish capital.
Judges have 'inherited' 150 unresolved corruption cases, some involving high-profile individuals
Spain is to sue Catalan president Artur Mas after he defied a court injunction not to hold a vote on secession, potentially barring him from running in regional elections
Despite the radical left-wing party taking the lead in the Spanish polls, over 50% don't see them as a realistic alternative to the two main parties
Hackers have targeted pro-independence campaign sites and local Catalan government web pages, while crank calls have kept organiser's line busy
"We have earned the right to a referendum," said Catalan leader Artur Mas, after two million people voted for independence from Spain
The 10-month-old left-wing party leads the polls, in the biggest ruction of the two-party system since the fall of Franco