BRASILIA, (Reuters) – Brazilian President Luiz  Inacio Lula da Silva may struggle to get a handpicked successor  elected next year after his choice was diagnosed with cancer.

Dilma Rousseff, Lula’s influential chief of staff, shocked  the political world over the weekend when she revealed that she  had had a tumor removed from her armpit and would undergo  chemotherapy to treat lymphoma.

Rousseff’s illness, coupled with a sharp economic downturn  that has begun to erode Lula’s lofty approval ratings, has  unleashed a fierce debate about next year’s presidential race  and could spark a power struggle among political parties.

“The two episodes can change the course of the election,”  Arko Advice, a Brasilia-based political consulting firm said in  a report.

Doctors say Rousseff, 61, has a 90 percent chance of a full  recovery after undergoing chemotherapy for the next four  months, a period that could be crucial for her to negotiate  support as she tries to claw back from trailing in early  opinion polls.

“It’s a brake on her campaign, the political negotiations  are on ice,” said Lucia Hipolito, a political commentator for  CBN radio.

Likely to benefit most from the episode is Sao Paulo state  Governor Jose Serra, who is emerging as the probable opposition  candidate for the Brazilian Social Democracy Party, or PSDB.

Serra, 66, lost to Lula in the 2002 presidential race and  has extensive experience in government. A political centrist  who served as planning minister and health minister in the  1990s, Serra has begun a slew of high-profile public works  projects in Sao Paulo in a bid to consolidate his lead on  Rousseff.

Earlier this year, Rousseff’s candidacy was endorsed by the  Workers’ Party founded by Lula, who by law cannot run for a  third consecutive term. She stepped up her campaign,  inaugurating public works projects, and even parading during  Carnival celebrations.

But the tough-talking former guerrilla lacks the political  skills and charisma that made Lula, 63, probably Brazil’s most  popular president ever, and she trails Serra by 30 percentage  points in opinion polls.