Although official preliminary results will not be published for days, leaders of rival Shi'ite parties acknowledged that Maliki's State of Law coalition appeared to be headed for a substantial win and perhaps a landslide in Shi'ite areas.
If confirmed, the results would amount to a crushing defeat for religious parties that have run Iraq's Shi'ite provinces with little heed to Baghdad since the 2003 fall of Saddam Hussein.
The prime minister would have strong momentum in his bid to hold on to power in national elections later this year in the majority Shi'ite country.
Until now, Maliki—who was installed by larger Shi'ite religious parties in 2006—had little clout of his own in the powerful regional governments that run cities and towns.
"According to initial information, (Maliki's) list has come first in Basra with 50 percent of the vote, (ours) took 20 percent," said Furat al-Sheraa, the head in Basra of the Supreme Islamic Iraqi Council (ISCI), the party that has controlled most southern provinces since the U.S.-led invasion.
A source at Basra's electoral commission said that the State of Law slate was indeed ahead in early counting in the city, Iraq's second largest and source of most of its oil exports.
A senior figure in the movement of anti-American cleric Moqtada al-Sadr also acknowledged victory for Maliki, both in the south and in Sadr City, Baghdad's giant Shi'ite slum and Sadr's main power base in the capital.
"The first results of the elections show that the list of Maliki has swept the other lists, especially in Sadr City and some southern provinces," the Sadrist figure said, asking that he not be named while discussing unofficial results.
"This is because the performance of other parties in power was bad. This made the people vote for Maliki. They're just trying to get the minimum demands of life, which is security, and Maliki succeeded in imposing it."
The electoral commission has asked the public to wait for its official results, which may not be definitive for up to a month.
Some politicians cautioned against reading too much from unofficial results. ISCI parliament member Jalal al-Din Saghir told Reuters it was too early to predict the outcome.
But anecdotal evidence also points to success for Maliki.
Straw Poll
Of dozens of voters throughout Sadr City interviewed by Reuters, nearly all said they picked the prime minister's slate.
At Sadr City's al-Chowadar coffee shop, a straw poll was unanimous. Everyone said they voted for "Abu Asraa", referring to the prime minister by his daughter's name.
"He succeeded in changing our bad situation for the better. We trust him," explained Haj Nassir al-Lami, an elderly man puffing on a water pipe.
Victory in Basra and Sadr City would mark an extraordinary turnaround.
Less than a year ago, both areas were controlled by Sadr's black-masked Mehdi Army fighters and saw demonstrations against the prime minister. Hundreds died when Maliki ordered a military crackdown, backed by U.S. helicopter strikes.
Notably, Maliki achieved his apparent election victory among Shi'ites despite a campaign that rigorously avoided religious slogans or imagery, which could help him with non-Shi'ites in the national election.
ISCI, by contrast, hammered on Shi'ite themes in the campaign. Its party Web site declares "Peace be upon you Hussein," referring to the grandson of the Prophet Mohammad whose followers formed the Shi'ite branch of Islam.
Maliki favours a strong central state, while ISCI and some other Shi'ite groups have sought greater autonomy for the south, where 80 percent of Iraq's current oil production comes from. The prime minister's success would undermine their autonomy bid.
But it could also herald pitfalls ahead.
His many rivals are bound to focus on cutting him back down to size, said University of London Iraq expert Toby Dodge: "If he comes out of this too strong, that will trigger a sustained move against him."
