Sen. Cory Booker, D-N.J., and Sen. Kamala Harris, D-Calif., listen as Dr. Christine Blasey Ford testifies during the Senate Judiciary Committee hearing on the nomination of Brett M. Kavanaugh to be an associate justice of the Supreme Court of the United States, focusing on allegations of sexual assault by Kavanaugh against Christine Blasey Ford in the early 1980s.

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.

Wolf, a former advisor to former President Barack Obama, including as a member of the President's Economic Recovery Advisory Board, said he had been in touch with 2020 hopefuls — but declined to name the individual lawmakers.

"I am meeting with possible candidates often but don't want to name names until he or she announces," Wolf said in a text message to CNBC.

However, people familiar with the talks say Wolf's contact list has included Gillibrand, along with New Jersey's Booker and California's Harris. Wolf has a history of backing the three senators. He wrote a check to Gillibrand for $2,700 in 2018 and donated to Harris' campaign in 2016. In 2014, he backed Booker's Senate campaign.

Wolf did not return follow-up requests for comment, and a spokeswoman for Harris did not return repeated requests for comment.

Booker also recently met with a top New York donor who described the encounter to CNBC on the condition of anonymity. "I had tea a while ago with Cory," this person said. "The meetings aren't officially about running, but of course they are about running in 2020." Booker seemed to be trying to see whether this financier could help raise money for a White House run, according to the person.

A spokesman for Booker did not reply to emails requesting comment.

Gray, a billionaire and top Democratic donor, has had numerous private discussions with Gillibrand and other lawmakers who might be looking to jump into the race, according to people familiar with the conversations.

Last year, Gray contributed $2,700 to Gillibrand's primary and general re-election campaigns, the most an individual donor can give directly to a campaign. In 2015, he donated the same amount to Booker. Gray also gave $600,000 to the Senate Majority PAC, a group dedicated to helping Democrats win the majority in the U.S. Senate, according to Federal Election Commission records.

Representatives for Blackstone and Gillibrand declined to comment.

Gallogly, another former member of Obama's Economic Recovery Advisory Board, has spoken with some of the same senators, according to people with direct knowledge of the exchanges. Gallogly has been in contact through email and other means with Gillibrand, and almost every other possible candidate considering a run for the White House, a person with direct knowledge of the matter said. The financier, however, has yet to hear from Harris and Booker about how they would craft a 2020 campaign, this person added.

Sen. Sherrod Brown, D-Ohio, a vocal critic of Wall Street who is considering a run for the White House, thanked Gallogly for his support in a voicemail after he won his re-election campaign in 2018, according to a person familiar with the outreach, but the two have not been in touch about the 2020 election. Gallogly gave at least $2,700 to Brown's campaign committee. Brown is the ranking member of the Senate Banking Committee.

A person close to Brown insisted that the senator has not been seeking Wall Street backers. The person added that the senator will continue to work the national fundraising circuit regardless of whether he runs for president, because Ohio is a battleground state that will be saturated with campaign ads. Trump won Ohio in 2016, after Obama won the state in 2008 and 2012.

"I can guarantee you Wall Street hates the idea of a Sherrod Brown White House," the person close to the senator said.

During a recent interview with CNBC's John Harwood, Brown criticized the influence Wall Street has on Congress.

"What's rotten on Wall Street is the influence the financial services industry continues to exert on Congress. Whenever they want something, they almost always get it," Brown said in November.

Gallogly and a spokeswoman for Brown declined to comment.