The California governor said Speaker Kevin McCarthy’s decision to open the investigation despite the GOP failing to uncover a direct link showing the president benefited from son Hunter Biden’s business dealings was a “joke”.
“This is student government,” Mr Newsom said in an hour-long interview with CNN’s chief political correspondent Dana Bash broadcast on Monday night.
“I mean, this is a perversity with what the founding fathers ever conceived of and imagined. So, if that’s the best they could do, give me a break.”
Mr McCarthy has claimed opening an impeachment inquiry is required to probe the millions of dollars earned overseas by Hunter Biden while his father was heavily involved in the Obama administration’s foreign policy.
Mr Newsom told CNN he didn’t “love” politicians’ family members using their influence in Washington DC to amass wealth.
But he added that it was “hardly unique” for family members to attempt to cash in that way.
“If that’s the new criteria, there are a lot of folks in a lot of industries, not just in politics, where people have family members and relationships that they’re trying to parlay and get a little influence and benefit in that respect,” he told Ms Bash.
In a wide-ranging interview, Mr Newsom quashed speculation that he would run for president and endorsed Kamala Harris to be the 2024 vice presidential nominee.
He praised the Biden administration’s legislative accomplishments as a “masterclass”, including its bipartisan deals on gun control, infrastructure and semiconductor manufacturing.
The interview came amid increasing calls for Mr Biden, 80, to step aside from the 2024 contest. A new Harvard CAPS-Harris Poll showed the president trails Donald Trump and several other Republican presidential candidates in a hypothetical general election match-up.
Concerns have grown about Mr Biden’s age and the drumbeat of negative publicity surrounding his son, who was indicted on gun charges last week.
In a separate Reuters-Ipsos poll, Mr Biden had an approval rating of 42 per cent, the highest it has been since March.
Mr Newsom called on Democrats to stop “this sort of navel-gazing about Joe Biden, and let’s get going.”
“Let’s get on the train. This train has left the proverbial station,” he said.
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