Spanish unemployment hit a record 5.64 million people and triggered angry marches across the country over Prime Minister Mariano Rajoy's austerity package.
Rajoy warned that Spain had no alternative to drastic public cuts and said it could face the fate of Greece, Ireland and Portugal, the three European bailout recipients so far.
Analysts said a Spanish bailout could be a crippling drain on EU resources and, combined with political uncertainty in France and recent economic downgrades of both France and Spain, the crisis could become too big to handle for the European Central Bank.
Standard and Poor's ratings agency on Thursday downgraded Spain's credit rating for the second time this year, reinforcing critics who argue that austerity alone isn't enough to ease the eurozone debt problem.
Hollande says if elected he would push for growth, in direct conflict with EU rescue policies.
Analysts said that with no short-term solution in sight the ECB would have to keep injecting cash into the banking system but without any commitment to stimulate growth -- the opposite of the EU-wide contraction the bank advocates.
Bank of Spain figures indicated the Spanish economy contracted 0.4 percent in the first three months of this year, after shrinking by 0.3 percent in the final quarter of last year.
Concern over jobs is also a major issue in French elections and, in addition to immigration and Islamic militancy, is seen as one of the reasons behind the vote for far-right candidates.
Hollande secured 28.10 percent of the vote in the first round, with Sarkozy trailing at 26.98 percent and National Front's Marine Le Pen capturing an 18.76 slice.
The May 6 runoff will feature only Hollande and Sarkozy and but the task before Sarkozy before the second round is to persuade Le Pen backers to switch to his side. Sarkozy faced sharp criticism this week for statements seen by critics as a cynical bid for winning over the far-right voters.
Hollande launched a counterattack and pledged to cut back foreign labor in France, appealing to a wider audience than Le Pen's far-right backers.
If Hollande goes through, as widely expected, the resulting change will instantly overhaul both political and financial dynamics of the eurozone. Le Pen's win has already introduced a major element of uncertainty for Hollande, who will face a strident right-wing opposition if he wins the runoff.
A French far-right victory is also a boon to other far-right political movements across Europe that have deep-rooted grievances against the EU. Some recommend radical measures -- from pulling their country out of the 27-nation EU or the 17-member eurozone, dumping the euro and switching back to national currency, to throwing out austerity plans and embarking on big spending, with unpredictable consequences.