* Northern support key to chances of first round win
* Kano second most populous city after Lagos
* Northern elites fear marginalisation
(Recasts with quotes, colour from rally)
KANO, Nigeria, March 16 (Reuters) - Thousands of ruling party supporters flocked to a dusty polo ground in Nigeria's northern city of Kano on Wednesday for the penultimate leg of President Goodluck Jonathan's election campaign tour.
Securing support in this ancient Islamic city, Nigeria's second most populous after the southern commercial hub of Lagos, will be key if Jonathan, who is from the southern Niger Delta, is to clinch victory in the first round of the April polls.
As the incumbent, Jonathan is considered the front-runner, but his main rival, Muslim ex-military ruler Muhammadu Buhari, has strong grass roots support in many parts of the north and the opposition is hoping to force a run-off.
"We will unite this country...and run an open government that does not discriminate," Jonathan told the crowd, eschewing his usual fedora and kaftan for a red cap and white robes, the traditional dress of the northern Hausa-Fulani ethnic group.
"We are encouraged by the crowd we see here," he said, on the 35th stage of his tour of Nigeria's 36 states.
From Islamic police enforcing a ban on beer and prostitution to its centuries-old market and mosques, Kano feels like a different country to the pulsating southern sprawl of Lagos.
Its dusty, tree-lined streets and throngs of child beggars have more in common with the sleepy Sahelian cities of Niger or Chad than with Lagos in the south, a city built on hustle and home to some of Africa's largest firms and richest tycoons.
Jonathan inherited power after the death of late northern President Umaru Yar'Adua last year and some in the northern elite feel his victory would rob them of what should have been another four years in power for their region.
Buhari's reputation as a disciplinarian won respect from some, who lament the extent to which corruption has spread, and sits well with the conservatism of Kano, one of only four states where uniformed Islamic police are used to enforce sharia law.
He ruled Nigeria between December 1983 and August 1985, an iron-fisted administration best remembered for its "War Against Indiscipline", a campaign against graft in which politicians were jailed and drug traffickers executed.
"Buhari has a clean mind. He is a very religious and Godly person," said Hajia Hadisa Mohammed, 85, buying textiles in Kano's Kwari market, a labyrinth of narrow alleyways packed with stalls made of wooden lattice and corrugated iron roofs.
Much is at stake in Kano and Nigeria's other northern cities. Jonathan must win at least 25 percent of the vote in two thirds of the states to clinch victory. The core north, along with opposition strongholds in the southwest, are seen as the most likely regions to prevent him succeeding.
Northern Muslims long pulled the strings of political power.
Four military rulers from the region led the country in the decade and a half before democracy was restored in 1999 but since the end of military rule, the upper echelons of the security forces have increasingly been staffed by southerners and some in the north fear being marginalised.
The south has the oil reserves and sea ports and is home to the headquarters of Nigeria's banks. Rapid economic growth has created a generation of independent wealth no longer so reliant on the political patronage once dispensed by northern strongmen.
On the streets of Kano, such rivalries are considered the preserve of the political elite. For most people in a region where industry and agriculture are in decline, more basic issues such as jobs and reliable electricity supply are the priorities.
"What we want is change. This government has failed us. Buhari is the only option," said Sagir Haruna at his market stall, surrounded by piles of fabric from India and China.
For many of Nigeria's 150 million people, scraping by on a few dollars a day, politics is a game played by the wealthy whose prize is control of oil revenues and government contracts and whose outcome has little impact on their daily lives.
Kano youths grabbed what they could from Jonathan's rally.
Moments after his convoy sped from the polo ground, there was a scramble to strip the podium on which he had spoken, scavenging valuable planks of wood, tearing material from the drapings and even ripping up the red carpet, part of which was offered to this correspondent for 1,000 naira ($6).
"I came with just my legs, but now I've got this," said Abubakar Sadiq, 21, carting off a large scaffolding poll.
"I will keep it in my house and think of Goodluck Jonathan whenever I look at it," he said, but then paused and added:
"Or maybe I'll sell it." (For full Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ ) (Additional reporting by Mike Oboh; Writing by Nick Tattersall; editing by Matthew Tostevin)