Tom Steyer, co-founder of NextGen Climate Action Committee, speaks during the Global Climate Action Summit in San Francisco, California, U.S., on Friday, Sept. 14, 2018. David Paul Morris | Bloomberg | Getty Images

Billionaire Democrat Tom Steyer is aiming to finish off his spending spree in the 2018 congressional midterm elections with a $16 million infusion across all of his political organizations, CNBC has learned. One of Steyer's aides, who spoke on the condition of anonymity, said the philanthropist and liberal activist is looking to splurge in the final 11 days of the midterms in order to continue his mission of helping Democrats unseat Republicans across the country. The $16 million is part of the $120 million that Steyer was planning to spend, the aide noted. A spokesman for Steyer declined to comment. Steyer has been working behind the scenes to boost Democrats through his Need to Impeach campaign and his super PAC, NextGen Climate Action Committee. His PAC has been one of the most active committees this election season. So far, the PAC has raised $42 million and spent $1.3 million backing Democrats, according to the nonpartisan Center for Responsive Politics. It's also put out more than $663,000 against Republicans.

Steyer himself has spent $41 million supporting Democrats running for Congress and gave at least $2 million to a PAC backing Democrat Andrew Gillum's efforts to become governor of Florida. It's unclear how much Steyer has raised for candidates through fundraisers and donations to other influential nonprofits or whether he will actually reach his own $120 million pledge. Some of Steyer's top Republican targets include Nevada Senate Republican Dean Heller and California House Republicans Dana Rohrabacher, Steve Knight and Mimi Walters. Democrats need to acquire at least 23 seats in the House in order to regain the majority. Data analyst Nate Silver's FiveThirtyEight gives Democrats an 83 percent chance of retaking the House. On the other hand, Silver's data shows Democrats only have a 17 percent shot at becoming the majority in the Senate. One of Steyer's overall goals has been to see President Donald Trump impeached, a message he's used to encourage voters to choose Democrats instead of Republicans in November. He called on voters to sign his Need to Impeach petition as the Senate prepared to confirm former D.C. Circuit Judge Brett Kavanaugh to the U.S. Supreme Court amid accusations of sexual assault.