Another question can be:
If the libertarians claim to be the strict constitutionalists they claim to be, then why do they put candidates who support the constitution (i.e., conservatives) in jeopardy by running a losing campaign against them?
Sounds as if they run on a "sour grapes" platform against other, more electable, conservatives.
There is no Constitutional authorization for the DEA, for the T and F parts of the ATF, for the NEA, for HUD, for the FBI, for the EPA, and a host of other federal agencies. Thanks to a Constitutional amendment, there is a basis for the IRS but many agree it is abusive, intrusive, retaliatory, and generally out of control.
When the Rs get down to business and start dismantling these things, you will begin to have a claim that the R party supports the Constitution. Furthermore, and despite the Constitutional authorization to do so, if the Rs manage to dismantle the IRS and replace it with a NRST or flat tax, the Ds will be demolished for years ... if the Rs have the wherewithall to do it. Put up or shut up - it's your stage now.
By the way, I voted for Rs over Ls in two key races, Musgrave (graciously) and Allard (reluctantly - he wants a national gun show "loophole" bill enacted), and voted for Rs over Ds in all races no Ls had entered.