Independence USA, the political action committee for billionaire and former New York City Mayor Michael Bloomberg, has spent an additional $9.5 million on ads aimed at defeating Republican California congressmen.

The ads target GOP Reps. Dana Rohrabacher and Steve Knight ahead of the Nov. 6 midterm elections. Reports say Bloomberg's PAC spent $4.4 million against Rohrabacher, while $5.1 million was spent on advertising in favor of Democratic hopeful Katie Hill, who is running against Knight.

A small amount is also going to promote Democrat Mike Levin, an environmental activist who is running to succeed retiring GOP Rep. Darrell Issa.

Democrats are hoping to win a majority in the House and need to gain 23 seats to reach that goal. Bloomberg has spent almost $100 million on House Democratic races for the 2018 midterms, according to Axios.

Bloomberg announced earlier this month that he had re-registered as a Democrat. The move could signal that he plans to run for the Democratic nomination to face President Trump in 2020.

Bloomberg was registered as a Democrat until 2001, when he switched to Republican to run for mayor of New York.

He served three four-year terms and registered as an independent in 2007. He said he registered as a Democrat as a check and balance against the Republican majority.