The agreement between the national committee of the Libertarian Party, and the Robert F. Kennedy, Jr. campaign to cooperate on fundraising, is illustrated by this tweet.
Federal campaign law lets individuals donate considerably more to a national committee of a party, than to any candidate for federal office. The deal provides that individuals who have already given the maximum amount to Kennedy can now also donate to the Libertarian Party. Then, the Libertarian Party contributes 90% of that amount to the Kennedy campaign. So both campaigns benefit. This sort of arrangement would not be needed if there were fewer campaign finance limits, or if the federal limits were non-discriminatory.