What is the real meaning of this sentence? Why Jackie and not Marilyn?

Rebecca

When he says "a Jackie" here, he is referring to women like Jacqueline Kennedy, who was a former First Lady of the United States and President John F. Kennedy's wife. "A Marilyn" in contrast refers to women like "Marilyn Monroe", a famous old Hollywood actress who was popular for her beauty. In other words, he is really saying that he since he wants to be a senator, he needs to marry someone smart and intelligent or "a Jackie", and not someone who just has good looks or is "a Marilyn". This is his way of breaking up with Elle because he thinks she is beautiful but not very smart.