Federal law does not define or officially recognize the act of a presidential candidate “suspending” their campaign instead of formally ending it.
CNN: “Practically speaking, if a candidate removes him- or herself from the race without the intent of re-entering at a later date, then there is not a big difference between ‘suspending’ a campaign vs. dropping out entirely. The end result is usually the same: the candidate is no longer seeking that particular office… That said, there are two main differences between ‘suspending’ and ending a presidential campaign: delegates and money.”
Candidates who suspend their campaigns usually get to keep any delegates they’ve won and can continue to raise money beyond what’s needed to retire their campaign debts. In contrast, candidates who actually drop out of a race, usually have to forfeit certain delegates and are limited in how they can raise future funds.
Slate: “The phrase has been employed at least as far back as the 1970s and continues to serve as the most popular way for candidates to end their primary bids without closing down their campaign committees.”