4th Amendment Violated in Florida & Texas

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.

So if this is the case - how can you have a checkpoint where you can't refuse to give a blood sample, semen sample, breathalyzer or anything?   Where's the probable cause?  Where's the evidence that a crime may have been committed and so a search needs to be performed?

http://www.wtsp.com/news/topstories/story.aspx?storyid=165079&catid=250

Probable Cause: "Facts or circumstances that would lead a reasonable and prudent person to believe a crime is, has been or will be committed and that the fruits of the crime are still present."  (From memory from my military police training verbatim from the law manuals.)

This is one point on which Oregon has done very well.  Police are not allowed to do checkpoints in this state.  Although, if you have an out of state license plate and get pulled over - you can forget it.  I see Arizona and California come cruising up I-5 well over 10 over the speed limit and go past State Police and - well - it's a done deal.  You see the look on their face of "MAN everyone in this state drives slow! I'm getting pulled over?  Really? For 15 over???"