Republican Donald Trump and Democrat Hillary Clinton each look to strengthen their front-runner status when five states hold presidential nominating races Saturday

Republican Donald Trump and Democrat Hillary Clinton each look to strengthen their front-runner status when five states hold presidential nominating races Saturday, as Trump tries to weather a barrage of blistering attacks from his party's establishment.

Trump, the controversial New York billionaire who has opened a substantial lead in delegates over his presidential rivals, will be vying to rack up more wins in Republican contests in Kansas, Kentucky, Louisiana and Maine.

Polling has been scarce in all four states, which together account for just 155 delegates, and the contests will be open only to registered Republicans. The exclusion of the independent voters who have helped Trump's surge adds an air of uncertainty to the latest round of state-by-state contests to pick nominees for the Nov. 8 election to succeed President Barack Obama.

Since winning seven of 11 contests on Super Tuesday, Trump has come under withering fire from a Republican establishment worried he will lead the party to a resounding defeat in November's elections.

Mainstream Republicans have blanched at Trump's calls to build a wall on the border with Mexico, round up and deport 11 million undocumented immigrants and temporarily bar all Muslims from entering the United States.

Mitt Romney, the 2012 Republican presidential nominee, called Trump a phony and a fraud who was playing American voters for suckers, and 2008 nominee John McCain, a U.S. senator from Arizona, said Trump's foreign policy views were uninformed and dangerous.

But the anti-Trump forces have a short window of about two weeks for stopping the caustic businessman, who has accumulated 319 of the 1,237 delegates needed to win the nomination at July's Republican national convention, outpacing second-place rival Ted Cruz, a U.S. senator from Texas, who has 226 delegates.

On the Democratic side, voters in Louisiana, Kansas and Nebraska will weigh in on Saturday on the race between Clinton, the former secretary of state, and Bernie Sanders, a U.S. senator from Vermont.

Polls show Clinton with a big lead in Louisiana, which has a large bloc of the African-American voters, who helped her roll up victories across the South on Super Tuesday, but the caucuses in less diverse Kansas and Nebraska could be more suited to Sanders. The three states have a total of 109 delegates at stake.

Clinton has opened up a big delegate lead on Sanders, who might have a tough time making up the difference. All states in the Democratic race award their delegates proportionally, meaning Clinton can keep piling up delegates even in states where she loses.