Top Republican 'struggling' with RFK Jr.'s nomination over Kennedy's vaccine views

Democratic Sen. Ron Wyden said in his opening statement that Kennedy has "virtually no knowledge or experience in handling these issues."

Kennedy is a longtime environmental lawyer who has not worked in public health administration or medicine.

Republican Sen. Mike Crapo, chairman of the committee, took a moment before Kennedy's opening statement to speak on Kennedy's background, noting his education from Harvard and the London School of Economics as well as his involvement in different advocacy groups.

Sen. Ron Wyden, the ranking member on the committee, used his opening statement to come out against RFK especially with his stances on vaccines.

The Democratic senator cited Kennedy's role with working with officials with Samoa during a 2019 measles outbreak. Wyden said 83 Samoans died in that outbreak.

"Americans can not afford to import this experiment to our great nation," Wyden said.

To win confirmation, Kennedy can only afford to lose three Republican votes -- assuming all Democrats oppose him.

So far, no Democrats have publicly said they'll be supporting his nomination.

Some Republicans to watch include Mitch McConnell, a polio survivor, and Bill Cassidy, who has said he believes Kennedy is "wrong" on vaccines.

Vice President JD Vance has been lobbying senators behind closed doors to support Kennedy, ABC News previously reported. A spokesperson for Vance did not respond to a request for comment.

According to financial disclosure documents, Kennedy's primary source of income in the past year was large sums of referral fees from multiple law firms, including one that is leading a civil lawsuit against Merck's Gardasil vaccine.

Democrat Elizabeth Warren, who sits on the finance committee that will be questioning RFK Jr., has criticized him for making "millions off of peddling dangerous anti-vaccine conspiracies."

Kennedy said he has resigned from his work with several law firms and that if confirmed he would no longer be involved in legal cases. But in a plan greenlit by federal ethics officials, Kennedy said he plans to retain his right to 10% of fees awarded in contingency cases with Wisner Baum, so long as the cases don't involve the U.S. government. The federal government is not a party in the civil lawsuit against Merck.

Read more about RFK Jr.'s involvement in the lawsuit here.

-ABC News' Anne Flaherty and Soorin Kim