Hillary Clinton is the favorite U.S. presidential candidate among millionaire voters and would win a head-to-head contest with former Florida Governor Jeb Bush, according to the third CNBC Millionaire Survey conducted in March that was released today. The survey, which polls 750 Americans with a net worth of $1 million or more, found that 53 percent of millionaires would vote for the Democratic ex-Secretary of State, compared with 47 percent for the GOP presidential hopeful, in a hypothetical general-election match-up. Clinton had the support of 91 percent of Democratic millionaires, 13 percent of Republican millionaires and 57 percent of Independent millionaires. (Tweet this) When asked about the broader field of candidates, Clinton got the most support, with 36 percent of millionaires. Jeb Bush came in second with 20 percent, followed by Senator Elizabeth Warren (D-Mass.) with 8 percent, and Governor Chris Christie (R-N.J.) with 7 percent. Read MoreThese are the real masters of the election domains Within the broader field, Republican candidates received a total of 49 percent of the vote, suggesting that the race could tighten as Republicans coalesce around a single candidate.

Clinton had the most support among younger millionaires, with 70 percent of millionaires age 48 or younger backing Clinton in a head-to-head race with Jeb Bush. Among millionaires age 70 or older, Jeb Bush wins with 57 percent of the vote. The poll revealed that females show more support for Hillary Clinton, while males show more support for Jeb Bush. Clinton wins 51 percent of male millionaires and 58 percent of female millionaires. Bush wins 49 percent of male millionaires and 42 percent of female millionaires. The CNBC Millionaire Survey skews more Republican than the broader voting population, which makes the support for Hillary even more notable. Of the millionaires polled, 34 percent were Independent, 31 percent were Republican and 34 percent were Democrats (a few didn't give an affiliation). "That's a pretty significant lead for Hillary at this time," said George Walper, president of Spectrem Group, the nonpartisan wealth-research company that conducts the poll for CNBC. "But it's early, and a lot of these folks are just getting to know the Republican candidates." Read MoreMike Huckabee launches 2nd White House bid Of course, support from millionaires may be more of a liability than strength in the current age of populist politics. Hillary has said she wants to "topple" the wealthiest Americans and has attacked CEO pay. Being seen as the favorite candidate of millionaires could clash with her efforts on the campaign trail to be seen as the advocate of the working class and poor.

"There may be some guilt by association with millionaires," Walper said. Millionaire voters also don't always predict winners, despite their presumed fund-raising power. Millionaires favored Mitt Romney in the 2012 election, with 61 percent of millionaires saying he was more "aligned" with their views, according to a Spectrem poll at the time. What's more, the richer millionaires—those worth $5 million or more—lean toward Jeb Bush. Among those worth $5 million or more, 52 percent supported Bush, while 48 percent support Clinton. Read MoreThe 2016 GOP lineup grows: What will it mean? When asked about the most important issues in the 2016 presidential election, the largest number of millionaires—22 percent—pointed to taxes and government spending. Political gridlock was the second most important issue for millionaire voters (21 percent), followed by foreign policy (19 percent) and the economy/unemployment (16 percent). Among Republican millionaires, taxes and government spending was by far the most important issue (33 percent), while for Democrats and Independents the top issue was gridlock. Millionaires are also concerned about inequality but are split on how to solve it. When asked the best way to reduce inequality in the U.S., the most popular response (50 percent) was to improve education, followed by better savings incentives for the less wealthy (48 percent) and higher taxes for the wealthy(44 percent). Only 36 percent cited "raising the minimum wage" as a solution. Among Democratic millionaires, the top solutions were education and raising the minimum wage: Among Republican millionaires, the top solutions were improved savings plans reducing unemployment benefits.