When candidates for US president drop out of the race, they "suspend" their campaign. The fact that they use that word makes me wonder if they can un-suspend it if they wished to?
Technically, they would be able to "restart" their campaign because Federal law and the parties do not consider them as having left the race. Even though they do not intend to restart the campaign, they have not "dropped out" of the race. If you look at the Republican primary ballots in many states (such as Maryland as a example) all the candidates are still listed on the ballot. In fact, there have been cases in which candidates suspended and restarted their campaigns. Ross Perot is the case in which the candidate suspended the campaign (expecting it to be permanent) without first announcing that it was for a limited time.
In June 2004, both candidates for president suspended most of their political activities in the days following Ronald Reagan's death, although they did not pull their advertising. Ross Perot abruptly suspended his campaign in July 1992—ostensibly for good—despite projections that he might win as much as 20 percent of the vote. Then, on Oct. 1, Perot re-entered the fray, citing those grass-roots supporters as a motivation.
What does 'suspending' mean? goes through the differences and explains the meaning.
Federal law does not have a specific definition of "suspending" a campaign and does not officially recognize the act of "suspending" a campaign. Herman Cain announced in December 2011 that he was "suspending" his campaign, but federal law considers him to be a candidate until he officially terminates or closes his campaign account or publicly states he is no longer a candidate.
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. Four years ago, Hillary Clinton, John Edwards, and Mitt Romney all "suspended" their campaigns, but their bids had effectively ended.
One notable exception: John McCain announced he was suspending his presidential campaign in late September 2008 so that he could return to Washington to focus on the financial crisis. However, McCain made it clear that the suspension was temporary and that he would eventually resume with the campaign.
That said, there are two main differences between "suspending" and ending a presidential campaign: delegates and money.
Federal law plays no role in delegate selection rules. It's up to the party to decide how to treat delegates won by a candidate who has suspended his campaign. In general, candidates who suspend their campaigns get to keep any delegates they've won, while candidates who drop out have to forfeit certain delegates, usually statewide delegates.
"Suspending" a campaign allows a candidate to publicly withdraw from a race while preserving the ability to raise funds beyond what's needed to retire debt. This may include the ability to continue to receive federal matching funds, if the candidate has previously qualified for them.
When candidates announce they are dropping out or ending their campaigns, they may then only raise money to retire any remaining campaign debts or to pay for other costs related to shutting down a campaign committee. They may not continue to amass warchests beyond that if they drop out.
However, if a candidate "suspends" his campaign but doesn't officially end his candidacy, federal law does not specifically prohibit that candidate from continuing to raise funds for purposes other debt retirement.
Candidates who "suspend" their campaigns as well as those who officially drop out must still continue to file disclosure reports, as long as they have an active campaign committee.