The 2020 race for the White House is just barely under way, but the latest CNBC Millionaire Survey shows some troubling signs for the incumbent President Donald Trump, including an energized base of wealthy Democrats and unsteady support from wealthy Republicans. Just 34 percent of America's millionaires say they would vote to re-elect President Trump if the election were held today. Among Republicans, Trump has lost more than one-third of wealthy voters, with only 62 percent of Republican millionaires saying they would vote for the president if the election were held today. Thirty-six percent of the overall vote was scattered among 10 different possible Democratic nominees, while 22 percent went to other Republicans.

The semiannual CNBC Millionaire Survey, conducted Nov. 7 through Nov. 19 by Spectrem Group, is representative of the affluent population in the United States. The survey analyzes the investment attitudes and behaviors of 750 investors with $1 million or more of investable assets. Respondents are required to be the financial decision-maker, or share jointly in financial decision-making within the household. In the survey, 39.9 percent of the 750 respondents identify as Republicans, 32.4 percent are Independents, and 25.7 percent are Democrats.

Twenty percent of respondents, including 18 percent of Republican millionaires, think President Donald Trump won't even be the Republican nominee for president in 2020. Eight percent believe outgoing Ohio Governor John Kasich will be the nominee, while 7 percent think it will be Vice President Mike Pence. That means that at least some Republicans believe the President could face and lose a primary challenge in 2020, or that he could be forced to leave office prematurely. More from Millionaire Survey: The biggest risk to millionaire wealth is Washington Despite new tax laws, wealthy may give more to charity On the Democratic side, 38 percent of respondents believe former Vice President Joe Biden will win the party's nomination. Republicans and Independents were more likely than Democrats to say Biden would get the nod, though he is still the most popular choice among his own party. Overall, 22 percent responded "Other," while 10 percent say Senator Elizabeth Warren (D-MA) will be the nominee. Not a single democrat millionaire thinks Oprah Winfrey will be the Democratic nominee, but 3 percent of Republicans and 3 percent of Independents do. No Democrats have officially declared their intention to run.

Wealthy Americans are an important, politically active group. The vast majority — 96 percent — say they voted in the midterm elections in November. Additionally, 20 percent of Republican millionaires and 36 percent of Democrat millionaires say they have contributed to a local, state, or national political campaign in the past two years. Eighty-eight percent of those who have donated to political campaigns believe the money was well spent, an indication that wealthy donors are prepared to open their wallets again in 2020.