RFK's road to becoming JFK's campaign guru in 1960 started in 1946 with JFK's run for a Congressional seat in a district in Massachusetts. JFK didn't want-or-need assistance from RFK, since he was already swamped with well-meaning relatives trying to help. And, RFK, just out of the Navy after being stationed in the Caribbean, didn't have any political experience. JFK patronized his younger (by 8.5 years) brother, and RFK was hurt, but he was determined to show his worth.
In the 11th Congressional District in Massachusetts, the real race was in the Democratic primary. RFK assigned himself the three poorest wards in the district (they were also the most hostile to JFK), and he knocked on doors and ate a lot of Italian food. RFK felt far more comfortable meeting real people face-to-face instead of dealing with politicians and advisers. JFK's victory in the Democratic primary was due in large part to RFK's efforts; RFK showed his mettle in wards that were in effect enemy territory, wards that JFK had written off. So, it was during the 1946 Democratic primary for the 11th Congressional District in Massachusetts where JFK saw that his brother could be of immense value to his political ambitions.
RFK was in the process of launching his career in the Justice Department (in the criminal division), and was reluctant to join JFK's Senate campaign, especially due to the family dynamics he expected to endure from both JFK and their wealthy-and-influential father, Joseph Kennedy, Sr. RFK convinced one of his friends from Harvard, Ken O'Donnell, to join JFK's campaign, but when Joe (the father) forced out JFK's long-time campaign manager over false claims of impropriety, O'Donnell called RFK and told him that he was the only one that could bring order out of the campaign's chaos. RFK knew that his presence would be the only way to get his father to back off from running (and perhaps ruining) JFK's bid for the Senate.
RFK's first task was to convince voters in Massachusetts that they needed to elect a new Senator; there was little to distinguish the moderate Democrat from the moderate Republican, and the U.S. was experiencing tremendous prosperity. RFK figured out that the main things that separated the two candidates was JFK's charisma/personal magnetism, and JFK's idealism didn't sound ideological. RFK wouldn't realize until later that he possessed the same characteristics as his older brother.
Among those working in the campaign was Lawrence O'Brien (who years later became the
Commissioner of the NBA), whose role was to be the ultimate detail man to complement RFK's grand overall strategy. RFK also got the campaign running full speed during the summer instead of waiting for the traditional post-Labor Day starting point. Joe was working behind the scenes to advance JFK's political career; the Boston Post, after Joe agreed to lend the editor $500,000, broke with Lodge, Jr. and officially endorsed JFK (JFK later acknowledged that what his father did was necessary in order to obtain that very valuable/indispensable endorsement).
"Ruthless" was the label that was attached to RFK starting with this campaign, and that label stuck. Those that got to know RFK saw, rather, that he was rude to others far more than he was ruthless, since in 1952 RFK was shy and not-quite-as assimilated as JFK. As far as RFK was concerned, he didn't care what was thought of him, he only cared about what people thought about JFK.
JFK's margin of victory was almost identical to the number of women that attended receptions hosted by JFK's & RFK's mother, Rose Kennedy; according to Lodge, Jr., those tea parties were the difference. RFK attributed JFK's victory mostly due to what he considered to be Lodge, Jr.'s shortcomings; he thought Lodge, Jr. was a very lazy campaigner/politician. RFK was always uncomfortable looking back, and he didn't give himself enough credit for the successes that occurred due his efforts-and-abilities. But JFK understood what RFK meant to his now-Presidential political aspirations, and RFK was back at the helm as JFK pursued the Vice-Presidential slot on the Democratic ticket in 1956.
In the end, it came down to JFK and Senator Estes Kefauver (TN), with JFK at one point just 15 delegates away from the nomination (it was very possible that Joe played a role in denying JFK the spot on the ticket). RFK concluded that he had been out-planned and out-hustled; up to that moment, RFK didn't know what it felt like to lose. But as RFK told JFK, the result was probably the best thing that could have happened in terms of positioning JFK for the Democratic nomination for President in 1960.
RFK agreed to help Adlai Stevenson in the general campaign against President Eisenhower, and RFK was so impressed with Stevenson after working with him for six weeks that he voted for Ike. RFK's actions on behalf of Stevenson were more like a journalist taking notes instead of a campaign partisan, which Stevenson found very off-putting and irritating. During the general campaign, most prominent Democrats concluded that JFK and RFK were (silently) rooting for a Stevenson defeat to bolster their chances in 1960.