What I'm writing is standard political doctrine. Granted, endorsements often are just attempts by a politician to collect a payback later, but endorsements in major races can and sometimes do make a difference.
Endorsements most often make a difference under the following circumstances:
1. The endorser has an active political machine and puts it to work on behalf of the candidate. That can be especially helpful if the endorser is a governor or the mayor of a major city who needs to have a political machine to get elected and uses it aggressively to back other candidates as well. If a person giving an endorsement gets lots of people to volunteer their time and make donations and make phone calls to friends and supporters, it counts a great deal. In addition, a “get out the vote” operation is inherently local, which means a local political leader can carry tremendous influence in actually getting their candidate's supporters to the polls.
2. The endorser represents an ideological cause. If that happens, the endorsement can cause people to say, “If A says B is okay, then A knows B well so I should take their advice.” We have seen that happening with Sarah Palin in several races and with Bob Vander Plaats in Iowa. It's also the role traditionally played by organizations such as Right to Life and the NRA.
3. Celebrity endorsements work. Sorry, but they do... I don't like it, but there are people who really **WILL** vote for a candidate because a prominent actor or musician or sports figure likes them. It doesn't make any sense to me, but it works, and I can't argue with facts.
At the very least, Fred Thompson's endorsement is category #3. Let's not minimize it — there are people who remember his TV show who don't pay attention to normal Republican politics and will listen, especially if he goes on TV ads and says things supporting Gingrich. I can't speak for the level of clout he still has in his home state and its political machine (i.e., #1 and maybe #2) so I will defer to others on that.
Is Fred to be Newt’s VP choice? That ‘screen presence’ would be a big bonus ... just sayin’