Washington, March 7 Ahead of the crucial March 15 Super Tuesday nominating contests, Republican Marco Rubio and Democrat Bernie Sanders notched a victory each in Puerto Rico and Maine respectively to keep the US presidential race competitive.

For Florida Senator Rubio his second victory on Sunday in the Republican race, that has been dominated by real estate Donald Trump and Texas Senator Ted Cruz, provides him a rationale to stay in the race.

Establishment favourite Rubio, who has been endorsed by South Carolina\'s Indian-American governor Nikki Haley and Louisiana\'s former Indian-American governor Bobby Jindal, is now counting on winning his home state Florida on Super Tuesday.

But Trump who has won 12 of the first 19 contests is leading Rubio by double digits in the 99-delegate, winner-take-all primary in Florida on March 15.

Cruz too has gained some momentum with six wins including two on Saturday, while Ohio Governor John Kasich, whose state also holds a winner-take-all primary on March 15, is still seeking his first win.

On the Democratic side Sanders\' victory in Maine caucuses was his third of the weekend after winning Kansas and Nebraska, though Clinton won in Louisiana.

Meanwhile, during a Democratic debate on Sunday on CNN in Flint, Michigan, Clinton and Bernie Sanders angrily clashed over auto industry bailouts, guns and ties to Wall Street.

Asserting that the economy is weighted against the middle and working classes, Sanders alleged that it was abetted by close ties between politicians, such as Clinton, and Wall Street financiers.

He also accused Clinton of supporting \"disastrous\" trade policies that contributed to corporate America\'s decision to move manufacturing from cities like Flint to low-wage economies in Central America and Asia.

Sanders repeatedly knocked Clinton for her ties to the finance industry and demanded that she release transcripts of her paid speeches to Wall Street firms.

Clinton said she will do so when other candidates, including Republicans, agree to do the same.

Clinton also claimed she had the most comprehensive plan to combat climate change. As secretary of state, Clinton said she worked with President Barack Obama \"to put pressure on China and India and other countries\" to join the global agreement in Paris.

Both candidates billed themselves as the best possible person to take on the Republicans, particularly Donald Trump, in a general election.

Clinton slammed what she said was the \"bigotry, bullying and bluster\" of the Republican front-runner, while her rival pointed to polls indicating he was more likely to beat the billionaire.

Meahwhile, Trump said on Sunday that, as president, he would push to change laws that prohibit waterboarding and other harsh interrogation techniques, arguing that banning them puts the US at a strategic disadvantage against Islamic State militants.

\"We have to play the game the way they\'re playing the game,\" Trump said in an interview on CBS Sunday, one day after he told an audience in Florida that he would fight to expand and broaden the laws that regulate interrogation.

\"I would like to strengthen the laws,\" he added on Sunday, \"so that we can better compete.\"

Sanders, Rubio wins keep US presidential race competitive