What does ‘Move the bar on somebody’ mean?

According to Maureen Dawd’s article titled “Field of Dashed Dream’ appearing on August 16 New York Times, President Obama took a strong verbal punch on the chin from a woman supporter at a town hall meeting at the Seed Savers Exchange in Iowa. She asked the President "what had gone wrong" with him, and continued:

“So when you ran for office you built a tremendous amount of trust with the American people, that you seemed like someone who wouldn’t move the bar on us. --- And it seems as if your negotiating tactics have sort of cut away at that trust by compromising some key principles that we believed in, like repealing the tax cut, not fighting harder for single-payer. Even Social Security and Medicare seemed on the line when we were dealing with the debt ceiling.”

I don’t understand what ‘move the bar on somebody’ mean. I checked the meaning of this phrase on the Google, but couldn’t find out any definition.

I think that the woman is coining metaphors based on the phrase, raise the bar. To raise the bar means:

to set a higher standard for other people to follow

So, if you raise the bar you are raising standards--the "bar" is a metaphor for those standards. To then say that someone is moving the bar implies that someone is shifting the standards around, and not necessarily for the better.

The woman is saying that, when Obama was elected, he promised to stand by X standards. Now, however, he has moved the bar on people and is now standing by Y standards. In other words, he is being weasely and not sticking by the standards he set.

I don't think this is standard English, so I wouldn't use it in conversation.

Edit: @Phoenix brings up the related metaphor moving the goalposts which is more common. It means:

changing the target of a process or competition by one side in order to gain advantage.

Unlike moving the bar on us, which may be more regional, this phrase seems a lot more common. A quick Google Ngram yields:

You could definitely use this phrase in conversation to describe this situation, and it is possible that because it is more common you would be more widely understood.

It's a misspoken version of "raise the bar", which originates from the high jump competition of athletics, when the "bar is raised" to the next height, making it harder to clear. In broader usage, "raising the bar" means that the minimum required standards in the context have been increased.

It's a conflation of "raise the bar" and "move the goalposts" -- both idioms from (sports metaphor) for changing the goal, generally to make the challenge harder.

"Raise the bar" has a connotation of fairness: the bar is raised as part of the larger contest as people succeed at the old way; akin to an old record being broken, so now people are trying to break the new record. ("Raise the bar" is often said of the person who achieved greatness by the old standard, and thus set the new standard.)

"Move the goalposts" (or goal line) has a connotation of unfairness: the goal was set, attempts were begun, and before they could be played out, the standards by which the outcome would be judged was changed.

In this case, I believe the speaker meant something more like the latter.