undermine somebody's credibility

In court last week, they began trying to undermine his credibility.

And he'd done everything in his power to undermine her credibility.

And that could undermine the credibility of American foreign policy for years to come.

So what are you being asked to do that will undermine your credibility?

A1 Bush said the 1990 tax increase undermined his credibility.

"They are beginning to undermine the credibility of the industry and their product."

The practices of the press were to further undermine its credibility.

The result has been to undermine the credibility of the Union in this sector.

To claim that could undermine our credibility in the future when we may have real cause for concern.

This is a problem for the entire Union and undermines our credibility on the issue of human rights.