Jonathan, a Christian from the south, became the ruling party's candidate three weeks ago despite an unwritten power-sharing rule that favors the candidacy of a Muslim northerner.
On Monday, he greeted the crowd in Lafia in the northern Hausa language and was flanked by his northern running mate, Nnmadi Sambo.
"The strategy is to commence the campaign in a less political state and de-ethnicize his campaign in order to show himself as a national leader," said Thompson Ayodele, executive director of the Initiative for Public Policy Analysis in Lagos. "Especially after the primaries that were embroiled in ethnic issues."
Jonathan carried more than two-thirds of the primary vote even though his main challenger had been chosen as a consensus candidate by the party's northern elite.
The choice between Jonathan and former vice president Atiku Abubakar highlighted the religious and ethnic fault lines running through Nigeria, a West African nation of 150 million people.
Jonathan became president only after last May's death of Nigeria's elected leader, Umaru Yar'Adua, a Muslim from the north who had only served one term. For that reason, some within the party believe this year's presidential candidate should have been another northerner.
Winning the endorsement of the country's ruling party made Jonathan the overwhelming favorite to be Nigeria's next president. The ruling party has won every election since the end of military rule in the oil-rich nation about a decade ago.
The upcoming elections, challenging the notions of power-sharing in the ruling party, could exacerbate tensions in Nigeria where recent violence in the northeastern state of Borno alone has left at least 40 people dead.