Los Angeles businessman Rick Caruso picked up an endorsement from another high-profile billionaire in the race to become the city's next mayor. 

Elon Musk tweeted Friday that he is backing Caruso in the contest to succeed Mayor Eric Garcetti. 

"It is rare for me to endorse political candidates," Musk said in a tweet.  "My political leanings are moderate, so neither fully Republican nor  Democrat, which I am confident is the case for most Americans. 

"Executive competence is super underrated in politics – we should care about that a lot more!" The endorsement comes with four days to go before the California primary election.

Caruso responded with a thank-you to the CEO of SpaceX and Tesla, and prospective Twitter buyer.  

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"Elon, thank you for your support," Caruso tweeted. "L.A. is the greatest city in the world. I would be honored to be her next mayor and serve the city that I love." 

Caruso is the founder and chief executive officer of Caruso, a retail  complex development company. He has been a member of the LA Department  of Water and Power Commission, Police Commission, and recently stepped  down from his role on the USC Board of Trustees to run in the election. 

Musk and Caruso are two of the wealthiest men in the world. Caruso’s  amassed a $4.3 billion fortune, largely because of SoCal shopping center  investments, 

which makes him the 655th wealthiest person in the world, according to Forbes. Musk’s $220.9 billion fortune, also a Forbes estimate, is beyond that of anyone else,  

Current LA Mayor Garcetti has termed out after first being elected to office in 2013. Garcetti is waiting for confirmation of his nomination made by President Biden to be the U.S. ambassador to India.