The Walloon Socialists are the largest party in the south of the country following the result of the general election held in June last year, which failed to produce a majority for any political party.
The other major winner at the polls was the separatist Flemish N-VA party led by Bart De Wever, which took 28% of the total vote.
Successive attempts to form a workable coalition have broken down, with the King asking a succession of negotiators (preformateurs) to produce a stable government.
Di Rupo, if he succeeds, would be the first French-speaking politician to be premier in 32 years.
For almost a year the country has been run by a caretaker government led by Yves Leterme, as negotiation after negotiation broke down.
However, recently the financial markets have warned that the failure to create a government could now cause panic, raising borrowing costs and affecting the long-term performance of Belgium’s soveriegn bonds, a device that helps service the country’s national debt.
The issues that have caused the deadlock are over the Flemish parties demands for more autonomy in fiscal and social policy for the Dutch-speaking population and a fierce language dispute in the Brussels-Halle-Vilvoorde region.
It remains to be seen whether Di Rupo has the skills to create a workable agreement for both north and south of the country. If he does succeed King Albert will be very relieved.