A new poll of 18- to 29-year olds by the Harvard Institute of Politics (IOP) finds that Hillary Clinton is the clear favorite in a hypothetical Democratic primary, while potential Republican primary voters have no definitive front runner, with more than a third of respondents undecided.

Clinton would get the support of 47 percent of potential Democratic primary voters. Massachusetts Sen. Elizabeth Warren, who has said she is not running for president but still has an ardent following, would get 11 percent support. Vice President Joe Biden, who has not yet declared a candidacy comes in third with 8 percent support, followed by former Maryland Gov. Martin O'Malley (3 percent), former Virginia Sen. Jim Webb (2 percent) and Vermont's independent Sen. Bernie Sanders (1 percent). Twenty-eight percent of potential primary voters say they are still undecided.

The most popular opinion at this very early stage in the cycle among potential Republican primary voters is no opinion at all, with 36 percent of prospective young Republican primary voters expressing no favorite candidate. The leader among the rest of the pack is Kentucky Sen. Rand Paul (8 percent), followed by former Florida Gov. Jeb Bush (7 percent), former Arkansas Gov. Mike Huckabee (7 percent) and Wisconsin Gov. Scott Walker, former Alaska Gov. Sarah Palin and Texas Sen. Ted Cruz tied at 5 percent. Other presumed and actual candidates all get four percent support or less.

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Of that group, only Cruz, Paul and Florida Sen. Marco Rubio - who received 2 percent support - have declared official candidacies.

"There are plenty of opportunities for Republicans to make inroads with this generation," said John Della Volpe, the IOP polling director.

The poll also probed attitudes about race, finding that young Americans are split on the question of whether they trust the American judicial system to judge people without a bias for race and ethnicity. Nearly half of young people, 49 percent, said they had "not much" or "no" confidence, while an equal percentage said they had "some" or "a lot" of confidence. Attitudes had some correlation with race, with a majority of young white Americans (55 percent) saying they had had some or a lot of confidence, while only 44 percent of Hispanics and 31 percent of African Americans said the same. Republicans also tended to be much more confident in the system, with 66 percent saying they had some or a lot of confidence people would be judged without bias for race and ethnicity, while only 46 percent of young Democrats said the same.

Other key findings from the poll include:

A majority of young Americans, 55 percent, say they would prefer the White House remain in Democratic hands after President Obama's second term ends, although a majority of young white voters say they would prefer a Republican president (53 percent).

There is an even split, 49 percent to 49 percent, on support or opposition to the national protests of police treatment of African Americans. Support once again had a correlation with race, with just 37 percent support from young whites, 59 percent support from Hispanics and 81 percent support from African Americans.

Eighty percent of young people say they would support mandatory body cameras for police officers on patrol when it is presented as a reform to reduce racial inequalities in the criminal justice system.

Nearly six in 10 young adults, 57 percent, say they would support sending ground troops to fight the Islamic State of Iraq and Syria in the Middle East. There is also growing support for the idea that the U.S. should take the lead in solving international conflicts, which jumped from 25 percent in March 2014 to 35 percent in March 2015.

Three in four young Americans believe global warning is a "proven fact," and just 23 percent say it is an unproven theory. But they are split on support for the Keystone XL pipeline, with 50 percent supporting and 48 percent opposing the pipeline. Nearly six in 10 young people oppose fracking, while 40 percent support it.

Eleven percent of women ages 18 to 29 who were surveyed in the poll said they have been victims of sexual assault. Two in 10 say they know a close friend or family member who was a victim. Five percent said they had been a victim and were also the friend of a victim.

After years of decline, young Americans are beginning to show more trust in the president, the military, the Supreme Court and the United Nations. Trust is up slightly in the federal government (25 percent), Congress (17 percent), Wall Street (14 percent) and the media (12 percent), though levels remain low.

Mr. Obama's approval rating is up seven percentage points over the past six months, giving him an approval of 50 percent among young Americans. He has seen an increase in support from all major subgroups, especially young Hispanics, where his approval is up to 65 percent in March 2015, from 49 percent in October 2014.

The poll is based on online interviews with 3,034 interviews with young Americans between 18 and 29 years old. The data collection took place from March 18 through April 1. The survey was conducted using KnowledgePanel, a probability-based panel designed to be representative of the U.S. population. Initially, participants are chosen scientifically by a random selection of telephone numbers and residential addresses. Persons in selected households are then invited by telephone or by mail to participate in the web-enabled KnowledgePanel.