Former US Secretary of State Hillary Clinton and businessman Donald Trump have maintained their leads among Democratic and Republican primary voters, respectively, according to the latest polls on the presidential races in both parties.

Republican Ben Carson and Democrat Bernie Sanders, meanwhile, ranked second among primary voters, the TIME reported.

The survey said Clinton leads her party's primary race, with 46 percent of the voters saying she is their choice for president. The former first lady is 19 points ahead of second place Vermont Sen. Bernie Sanders, and far ahead of Vice President Joe Biden who garnered 16 percent of the votes even though he has yet to officially declare his intention to run for the presidency.

Clinton's lead over Sanders could widen to 56 percent should Biden become a candidate for the party, the survey said. Six in 10 Democrats also find Clinton the most electable candidate, as 51 percent of women and 48 percent of older voters go in her favour.

Trump, meanwhile, tops the Republican Party race with 27 percent of primary voters on his side. His closest rival, Ben Carson has been soaring in polls, getting 21 percent of the voters' support in the latest poll. The rest of the Republican pool clocks in at single digits, with Texas Sen. Ted Cruz at third place at 9 percent, according to TIME.

Seven in 10 Republican primary voters say they would support Trump if he becomes the party's presidential nominee, while 35 percent of the voters think they could see Trump winning in the November 2016 election.

A majority of Republican voters or 42 percent, however, are reportedly not enthusiastic or have reservations about Trump's running for the presidency. About one in five prospective Republican voters say they will not support Trump if he becomes the nominee.

The TIME telephone poll allowed participants to rank the candidates on a variety of traits, including trustworthiness and leadership qualities. Trump topped in leadership qualities, with 65 percent of voters seeing him as a strong leader. Sixty-one percent of voters saw Biden as honest and trustworthy; Ben Carson ranked third with 58 percent.

For the category of candidates who are especially caring of voters' need, the poll shows Biden as the most favoured candidate, getting 67 percent of votes, and Carson with 63 percent of the votes. Trump reportedly scored the least in this category.

Biden is also the overall pick as the best candidate for President. At least 60 percent of voters think he has the best qualifications to be in the White House in 2016.

The telephone poll was conducted last week, with a margin of error of 6 percentage points among Democratic voters and 5 percentage points among Republican voters, the TIME report said.