The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
Searching bags around a major political event would not imo be considered "unreasonable"
Let me offer the following explanation to the contrary.
Just as the first part Second Amendment states the reason for the Second Amendment (A well-regulated militia, being necessary to the security of a free State) the first part of the Fourth Amendment does the same. (The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated,)
The second part of the Second Amendment then states what the mechanism will be needed to secure a free state: "the right of the people to keep and bear arms, shall not be infringed."
The second part of the Fourth Amendment then states what the mechanism will be needed to prevent unreasonable searches and seizures: "no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."
That being the case, I would say there is no way that the founding fathers would have left "quite a hole" in the wording of the Fourth Amendment as the undefined word "unreasonable" being the sole justification for a search and seizure of a citizen without a warrant.
Government needs to have a warrant, supported by oath or affirmation (probable cause) before government can search a citizen's person/property or seize a citizens property.
Thus, all searches and seizures by "federalized" security personel at airports are unconstitutional.
Any "blanket" search of citizens by government employees, (police, SS, IRS, DEA, TSA, FBI, BATF, etc) on public or private property without a warrant is unconstitutional.
Any "blanket" search by a private property owner by private property owner personel is perfectly legal because the constitution has no jurisdiction on private property over actions by private citizens.