Robert F. Kennedy Jr.’s path to becoming the next U.S. health secretary is anything but smooth. With most Democrats expected to oppose him, his fate lies in whether he can persuade skeptical Republicans to back his nomination. The stakes are high, and the spotlight is on a few key GOP senators who could make or break his confirmation.

One figure to watch is Senator Mitch McConnell of Kentucky. As the only polio survivor in the Senate, McConnell has a personal connection to public health issues. While he hasn’t openly criticized Kennedy, he’s signaled that anyone who questions proven medical treatments might struggle to gain Senate approval. McConnell hasn’t met with Kennedy for the customary pre-hearing visit, leaving his stance uncertain.

Another critical player is Senator Bill Cassidy of Louisiana. A doctor and chair of the Senate health committee, Cassidy wields significant influence over health policy matters. After meeting with Kennedy, Cassidy described their conversation as “frank”—a term often hinting at unresolved disagreements. He’s been vocal about his concerns, even stating publicly that Kennedy is “wrong” about vaccines.

Kennedy’s nomination faces an uphill battle in a closely divided Senate. With Republicans holding a slim majority, he can only afford to lose three GOP votes if the nomination reaches the full Senate. As the hearings unfold, all eyes will be on these key Republicans to see if Kennedy can win them over—or if his bid will fall short.