In an article (Reuters) about Barack Obama's focus on the general election Jeff Mason writes:
Obama praised Clinton, but spoke of her in the past tense in another sign he has shifted focus past the primary season.
I would expect the proof quotes to be something like this:
Senator Clinton campaigned valiantly.
Senator Clinton ran a tenacious campaign.
The crafty Clinton campaign gave me a good challenge.
Hillary Clinton was a fine opponent. She did not win this nomination.
Here are the quotes Mason used:
She has been a formidable candidate.
She has been smart and tough and determined and she has worked as hard as she can.
She has run an extraordinary campaign.
These are quotes that any candidate can make at the beginning in the middle or at the end of a campaign. There's no grammatical evidence that Obama is speaking of Clinton as something only behind him. If I say I've had a headache for three hours now am I saying that my headache is over? Even if I say it without the now and I mean that in that past I have had such a headache (as if to say that in the past at least one of my headaches lasted for three hours) I'm still not speaking in the past tense.
Linguification is commonly diagnosed with a comorbid disorder: a false claim about the grammar itself. Not a single one of Obama's statements is in the past tense. They're in the present perfect. Every one of them.
I don't really mind linguification. While I agree that grammar choices aren't proof of mindset there are times when grammar or word choice can indicate something about attitude. The past tense is commonly noted as doing so. When someone dies people start choosing carefully phrases like he meant/means a lot to me or she was/is my favourite aunt. The choice is often commented on by the speaker. Refusing to use the past tense can be a way of saying that the dead loved one is still important and their life is still relevant. Or something like that.
But before you try to haruspicate the reasons for choices you really should know what was chosen.