It has recently been in the news that both Ben Carson and Donald Trump are asking for Secret Service protection. There is a specific process in place to determine who and when Secret Service protection is granted.
Basically it starts with a request to the Director of DHS and is then reviewed by congressional leadership to determine if a presidential candidate has enough support among the electorate and that there may have been or is likely to be, various threats against a candidate. The question of does the government have the resources to provide protection is never an issue.
There are pros and cons to having protection. The obvious advantage is that it does give a candidate “street creds” in terms of their viability and protection is usually a good thing given the multitude of crazies running around.
The disadvantage is that the personal interaction between a candidate and the public early in the campaign can be somewhat limited once the protective bubble is put in place.
President Obama received protection earlier them most in the 2008 election due in large part to his African-American heritage. As the press reported then many threats were coming in from various hate groups as well as lone wolves. The Service was bound and determined not to have an assassination attempt on him and obviously was successful.
Personally I find it interesting and, if I were a Secret Service employee, very frustrating, to be ask time and time again to put forth extraordinary efforts, work 12 hours a day under extreme stress, and then be a part of an agency whose staffing is cut by 500 people due to sequester.
Sequester was implemented to hold down government expense while the Congress could not agree on spending cuts or revenue increases. It was designed to be draconian in nature to force Congress to act. Once they could still not agree it became apparent that the military needed to be exempted from the draconian cuts and processes were developed for them to get around sequester. However, the more then 50 federal law enforcement agencies were not exempt. This included the FBI (remember they are in charge of protecting us from terrorism in the US), The Border Patrol (remember what they do? ) and of course the Secret Service, who by most accounts are down about 500 staff.
So as candidates clamor for protection we need to remember this stuff does not come free. If there were ever reasons for Congress to get its act together this is it.