BRUSSELS (Reuters) - The European Parliament will elect a new speaker next week in an unusually heated vote that could end a decade-long cooperation between mainstream parties, complicate lawmaking and trigger a reshuffle of top EU jobs.

All eight political groups of the legislature have fielded candidates, but the winner is expected to be one of the two Italians put up by the main center-right and center-left groupings.

Conservative Antonio Tajani, 63, a close ally of Italy’s former prime minister Silvio Berlusconi, is the favorite as he can count on the support of the European People’s Party, the largest grouping in parliament.

However, unlike past appointments which were agreed in advance by the main parties, he faces a real challenger in Gianni Pittella, 58, who is bidding to succeed predecessor Martin Schulz, also of the center-left.

Breaking from a decade-long convention whereby the major groupings take turns to hold the high-profile job, Pittella has vowed to stimulate genuine debate and to dispel the idea that all main parties in the Parliament are part of a reform-shy establishment.

Pittella also argues that a deal to make Schulz, a German Social Democrat, head of the parliament in 2014 implied that the Socialists were entitled to hold at least one top EU job.

If Tajani wins, the conservatives would hold all three top posts. Jean-Claude Juncker of Luxembourg heads the EU’s Brussels-based executive, the Commission, and former Polish prime minister Donald Tusk chairs the European Council, which groups the national governments.

Socialists have warned that if Pittella does not win in the Parliament, they will push for a reshuffle of the key posts.

Tusk’s mandate ends in May but he is expected to want to stay on. Juncker has three years left, but has been weakened by Brexit, the migration crisis and recurrent criticism over Luxembourg’s tax deals with multinationals during his nearly 19 years as the country’s prime minister.

BOOST FOR EUROSKEPTICS?

The vote is scheduled for Tuesday and the 751 EU lawmakers might take up to four rounds to select the president.

Whatever the outcome, the divisive vote may make EU lawmaking more complicated, potentially delaying important pieces of legislation on financial services or the internal market over which the EU Parliament has a say.

A fragmented and inefficient parliament risks giving a further boost to euroskeptic forces, which are also likely to play a key role in electing the new president.

Tajani may need the support of French MEPs from Marine Le Pen’s far-right Front National or those of Nigel Farage’s United Kingdom Independence Party (UKIP) to be elected, giving them unprecedented negotiating power.