Monte dei Paschi  (BMDPY) , the world's oldest bank, secured the backing of shareholders for its latest bailout on Thursday. But despite the sigh of relief that might of whisked through the hallways of the bank on Thursday night, Monte dei Paschi's biggest challenge is still ahead. 

The vote gives the board the authority to push forward with a JPMorgan Chase  (JPM) -led rescue plan that will see it raise €5 billion ($5.3 billion) of new equity -- nearly 10 times its market capitalization.

The floundering Italian lender has crumbled steadily over the years since the financial crisis, under strains of a growing pile of nonperforming loans and weak profitability -- leading to no less than four separate bailouts.

The rescue plan, which has been pitched as a full and final solution to the bank's woes, will also involve a debt-for-equity swap that requires a number of unsecured creditors to take haircuts equivalent to around 15% of par value. In total, around €3 billion of debts are expected to be converted into equity.

Shareholder backing brings the bank one step closer to being back on a sustainable footing, but it doesn't mean that it is out of the woods.

The bank must still find buyers for its €27 billion nonperforming loan portfolio and persuade investors to back it with as much as €2 billion of new cash equity -- no easy feat when its market value is little more than €700 million.

It remains to be seen whether investors have the appetite for the cash call, given a looming referendum on constitutional reform in Italy that could quite possibly topple the government if its campaign to secure support for the reforms fails.

Monte dei Paschi will now need to convince new investors of its long-term viability if it is to secure the support it needs.

The Italian referendum is set for Dec. 4.

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