Is it a lie if a politician promises something, but does not deliver?
Or, is there something discernible about the language within the promise that indicates deception?
Remember, the words of President Bush when he said, "Read my lips, no new taxes."
He did not say "I will not raise taxes", using the strong pronoun, "I", rather than the weaker "we" in the statement.
He did, however, weaken the assertion "no new taxes" via the use of emphasis: "read my lips", first, and then secondly, "no new taxes" is passive language, avoiding ownership.
Here is an article from the NY Post on a book exert on the top lies of President Obama. Some sensitivity will be seen in deliberate repetition of a statement.
A promise, or campaign pledge, is deceptive if the subject does not intend to fulfill it. Sometimes, this is due to political gridlock or other unforeseen circumstances.
We are looking for that which is propounded without purpose of fulfillment. We also look for deception via tangent, or "red herring" to be followed away from the issue.
Note these tactics as well as passivity in order to discern.