Wall Street executives have heard from several potential 2020 Democratic candidates for president, including Sens. Cory Booker and Kamala Harris, as recently as last month, CNBC has learned.

The latest developments come as the Democrats' campaign to unseat Republican Donald Trump begins a year before the first contests of the presidential primary season, with contenders attempting to line up backing from donors and fundraisers.

The revelation of communication between Wall Street donors and possible Democratic candidates threatens to exacerbate tension between the liberal wing of the party, which is increasingly outspoken against the influence of corporate money in politics, and moderates who are seen as more business-friendly. A CNBC report last week about New York Sen. Kirsten Gillibrand's outreach to Wall Street triggered outrage on the left.

Billionaire and Blackstone Chief Operating Officer Jonathan Gray; Robert Wolf, CEO and founder of economic advisory firm 32 Advisors, and Mark Gallogly, a founder of private investment firm Centerbridge Partners, are just a few of the Democratic financiers who have spoken with 2020 hopefuls about a wide range of topics, including the upcoming campaign, according to people with direct knowledge of the matter.

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