Ghost-written speeches, slush funds and the IMF
Part of the erosion of political choice revolves around the fact that democracy is essentially a big popularity contest. It's easier for a slick leader to get elected than a truly smart one; Tony Blair and George Bush are both slick rather than great leaders. The men who truly control many of the actions of our governments are often no more visible than the advertising executives who write the scripts for television commercials.
Ghost-written speeches are not, as one might expect, speeches written by dead people. A ghost writer is often employed in order to allow a complete moron to appear more accomplished as a speaker. Other weapons in the quest to get idiots elected include hair transplants and excessively complex electoral systems.
A ghost writer will, of course, always have a political agenda of their own; if the writer is not keen on the politician in question, they may engineer a speech to make them look stupid.
Advertising agencies are often intermediaries in finding a writer to produce speeches for nascent politicos; Saatchi and Saatchi are famous for this. It is safe to assume that the skills involved in advertising are similar to those involved in the production of a political speech.
In some cases, such as speeches given by spokespeople and beauty pageant victims, the person reading the speech may have no choice over whether they read it or not; it may be a contractual obligation.
How to spot a ghost-written speech
The first thing to look for is similarities with other speeches. I'm not talking about quoting here; it's a fact that many high-volume writers have template speeches made up which are simply modified for a given occasion. (Politicians are sometimes fed speeches by civil servants; Yes Minister is a definitive work on this subject.)
The second thing to look for is facial expression. Many politicians, particularly busy ones, will not have had a chance to read the speech through in final draft before presenting it; after all, this is why they use autocue. Look for uncertainty and glassiness in their facial expression, resolving at the end of every sentence; this is a subconscious reaction to the fact that they don't know what each sentence says until they've got to the end.
The third thing to look for is long pauses between sentences. The reason they do this is to allow themselves to read each sentence before saying it; this avoids the second point, and if they're astute, can go some way towards skipping the first too.