Italy faces a political crisis after an ally unexpectedly resigned from the governing coalition led by Prime Minister Romano Prodi, leaving his coalition without a parliamentary majority. Prodi is expected to address the Italian parliament Tuesday, and may resign if he loses a confidence vote, paving the way for new elections.

Prodi took office after defeating Silvio Berlusconi, a staunch ally of the Bush administration and Italy's richest man, in a close election in April 2006. His coalition's razor-thin majority in the Senate has since been tested by scandals and policy setbacks. Mr. Berlusconi, who leads the center-right opposition and is currently ahead in opinion polls, has called for early elections if the government falls.

The Wall Street Journal says that the crisis follows the resignation last week of Justice Minister Clemente Mastella, who is being investigated, along with his wife, in a corruption case. Mr. Mastella, who leads a minor political party, said Monday that he was abruptly withdrawing support for Prodi's coalition because he wasn't getting enough political backing in fighting that corruption case.

While it is still possible Mr. Prodi could eke out a majority by courting new votes, it seems more likely he will have to hand in his resignation to President Giorgio Napolitano. A collapse would raise the question of whether this government's most important success – taming Italy's runaway deficit – will melt away in the political pandemonium that could ensue.

Hours before the political crisis broke, Agence France-Presse reported that Prodi had planned to meet President Bush during a scheduled Feb. 3 visit to the United States, his first since taking office. The two leaders held talks last year in Rome after Italy agreed to increase its troop commitment in Afghanistan.

Relations between the two countries had been frayed by Italy's pullout from Iraq and the fallout from Italian judicial probes involving US military personnel, reports AFP. One case involved the death of an Italian intelligence agent in Baghdad in 2005 after he rescued a kidnapped Italian reporter. Their car was allegedly fired on by a US soldier at a mobile checkpoint. A Rome court ruled last October, however, that it didn't have jurisdiction to try the accused US soldier.

In recent months, Prodi has steadily lost popular support in Italy despite delivering economic growth and cutting unemployment, Bloomberg reports. Divisions within his government, Italy's 61st since 1945, have sapped his poll ratings. A Dec. 23 survey found that 30 percent of Italians had confidence in him, down from 45 percent a year earlier.

Prodi has survived previous rifts in his coalition, and briefly tendered his resignation in 2007, says Reuters. The resignation resulted primarily from differences about the Afghan war and Italy's ties to the US military, reports the CBC. But the defection of Udeur – the Roman Catholic party led by Mastella – is the first by a major ally and potentially a fatal blow.

Prodi could still win votes in the upper house – where until now he [has] had a two-seat majority – with the support of seven unelected lifetime senators as he has done in the past, though their vote cannot be taken for granted.

The Financial Times reports that President Napolitano is said to oppose holding new elections until lawmakers make changes to the election system. The current system enacted in 2006 has been criticized for its bias towards small parties which yielded a weak and divided nine-party coalition. As the leader of a minor party, Mastella would favor holding early elections before the system is reformed, the FT says.

Prodi, a former economics professor, previously led Italy from 1996 to 1998. His resignation may not trigger automatic elections, though, as the president can give him additional time to gather his coalition together and survive a no-confidence vote, reports The New York Times. That was the case during the 2007 foreign-policy defeat that nearly toppled the government.

Another possible option is that Mr. Napolitano could call for an interim government of technocrats to oversee state business until elections could be called, presumably after a new election law is enacted.

A referendum on such a law was given court approval last week and, in theory, voting must take place before June 15. But many politicians dislike the proposed law because it would take power away from the many small parties in Italy, and it is possible that any interim government might seek to pass its own law before the referendum took place, thus negating it.

A further political challenge to Prodi's government is the outcry over trash collection in Naples, reports Italian news agency Agenzia Nazionale Stampa Associata. Environment minister Alfonso Pecoraro faces a no-confidence in parliament this week over his handling of the crisis, and may not get the support of coalition partners. Authorities have failed to collect garbage in Naples and the surrounding region of Campania after its waste-management system broke down, prompting public protests.

The Associated Press reports that collectors in Naples stopped picking up garbage after Christmas because city dumps were full. A former national police chief has since been tapped to take charge of the situation, which has snowballed amid allegations of mafia involvement.

The region has long been plagued by garbage crises: Dumps are overflowing and local communities have blocked efforts to build new ones or reopen old ones, citing health risks.

Officials and residents say the crises stem from the Neapolitan Mafia's control of garbage disposal and the government's inability to fight it or guarantee safe waste treatment. As a result, residents angered by the uncollected trash also routinely protest attempts to open dumps, often resorting to violence.