As a follow-up to my appearance on Matt Allen tonight, I thought it worthwhile to provide a link to VotersUnite.org, which I mentioned to Matt. As I said, they indicate that there are only 15 states that provide the straight-party option, though there are some caveats. For instance:

[1] North Carolina:
A straight party vote DOES NOT include the President. The ballot says:
“The offices of President and Vice President of the United States are not included in a Straight Party vote. This contest must be voted separately.”
[2] Oklahoma:
Ballots often have straight-party voting options in multiple places on the ballot. A straight-party vote applies ONLY to the set of offices it precedes on the ballot. This means to vote straight-party in all contests, you must mark several separate straight-party selections.
So, for example, as this Tulsa County sample ballot shows, you can vote straight-party for one or more of: a) Presidential office, b) State Officials, and c) Congressional Officers. A straight-party vote for the Presidential office WILL NOT count for the state and congressional officer contests.