Graham said that it would be the 'beginning of the end of his presidency'.
It's a threat of some sort. Under the circumstances, impeachment would be the most obvious threat. Graham's lack of specificity only feeds the idea that it's the most obvious threat.
Agree. But Linda didn't say the obvious - he's a weasel who's giving himself some wriggle room to appear to be "bipartisan". He's a wimp.