By Anthony Boadle

BRASILIA (Reuters) - Brazilian President Dilma Rousseff is coasting into an election year as clear favorite, but she must do more to curb violence and corruption to maintain her popularity, a poll showed on Thursday.

Rousseff has been recovering from the pounding her approval ratings took after the massive protests in June against corruption, poor public services and the high cost of living, according to the poll commissioned by the private transport sector lobby CNT and conducted by pollsters MDA.

The survey showed Rousseff defeating her most likely challengers in the October election without a runoff. Environmentalist Marina Silva, who was not able to register her party in time, would come closest to forcing a second-round vote.

Rousseff's strategy of more public appearances around the country is paying off, along with her plan to bring in foreign doctors to fill gaps in the national health system, CNT president Clésio Andrade said.

Increased public perception that inflation is under control also helped Rousseff edge up her personal approval rating to 58.8 percent in November from 58.0 percent in September, while her government's rating rose to 39.0 percent from 38.1 percent.

Rousseff will have to keep a close watch on prices, though. Data released on Thursday showed inflation slowing for a fourth consecutive month in October, but with the prospect of picking up speed due to higher food prices.

The CNT poll confirmed results of other recent public opinion surveys showing Rousseff has overcome the dramatic drop in support she suffered after the outburst of social discontent that saw hundreds of thousands of Brazilians take to the streets to vent frustration with their politicians.

Rousseff, a pragmatic leftist who is expected to seek a second term next year, has been rushing around opening public works projects to upgrade Brazil's dilapidated infrastructure and improve urban transport, a major source of social anger.

CUBAN HELP

She has also launched a program that will deploy thousands of foreign doctors, mostly from communist-led Cuba, to practice in poor neighborhoods and remote parts of Latin America's largest nation that have no resident physicians.

A growing majority of Brazilians support the program that was initially opposed by local doctors, according to the poll - 84.3 percent in November, up from 50 percent when the so-called "More Doctors" plan was launched in July.

If the elections were held today, Rousseff of the Workers' Party would win 43.5 percent of the votes against 19.3 percent for her closest likely candidate, Aecio Neves of the main opposition party PSDB, and 9.5 percent for Eduardo Campos, the little known but popular governor of northern Pernambuco state.

If Rousseff ran against her biggest potential threat, former environment minister Silva, her advantage would drop to 40.6 percent versus 22.6 percent. Silva, who won 20 million votes in a presidential bid in 2010, last month joined Campos' PSB party to keep alive a possible run after electoral authorities barred her from registering her party.

Brazilian polls are not considered of much use until TV campaigning begins three months before the elections and voters really start to pay attention.

A large majority of those polled defended the right of Brazilians to protest in the streets, but 93.4 percent said they opposed groups of masked agitators that have hijacked recent demonstrations and clashed with police.

The poll showed nine out of 10 Brazilian are "very worried" with violence in a country that has alarming crime and murder rates. "The government must take tougher action to curb this violence," Andrade said.

The poll of 2,005 people was conducted between October 31 and November 4 and has a margin of error of 2.2 percentage points.

(Reporting by Anthony Boadle; Editing by Vicki Allen)