Robert F. Kennedy Jr.’s impending announcement of his running mate is threatening to roil the 2024 presidential race, with allies and observers saying it could give him a cash influx as well as a major boost of momentum as he looks to get on more state ballots.Kennedy’s decision to unveil his vice-presidential pick next Tuesday shows a longevity to his bid that many Democrats hoped would have fizzled out by now. Announcing a running mate means the independent candidate has met a necessary benchmark required by two dozen states to be listed on the ballot, something that will bring even more attention to his campaign.