Senator Mark Kirk of Illinois, one of the most vulnerable GOP incumbents of the cycle, this week became the first GOP lawmaker to actively retract his endorsement of Donald Trump, over his racist attacks on a Mexican-American judge. Given that this move is itself an admission of just how toxic Trump is becoming to fellow Republicans, Kirk is a kind of test case as to whether it is even possible to un-endorse the Donald and get away with it.

The Dem-allied group American Bridge is out with a new Web video that attempts to hold Senator Kirk accountable for having backed Trump in the first place. It should be viewed as a template for paid ads that will try to use Trump as ammunition against GOP lawmakers this fall — whether or not the lawmakers in question did or did not try to actively escape Trump:

American Bridge 21st Century publishes an ad attacking Sen. Mark Kirk (R - Ill.) for retracting his support of Donald Trump for the Republican presidential nomination. (American Bridge 21st Century)

The ad simply informs viewers that Senator Kirk did in fact endorse Trump, and then shows footage of Trump insulting and belittling Mexican immigrants, insulting and belittling John McCain’s war record, insulting and belittling a disabled reporter (anyone else notice a pattern here?), and calling for a ban on Muslims entering the U.S. The ad also shows Trump previously questioning whether Judge Gonzalo Curiel could be impartial, given that he is “Hispanic.” The implication, obviously, is that Kirk endorsed Trump in spite of all those controversial positions, and in spite of his previous attacks on Judge Curiel, and only un-endorsed after the media heat grew so severe around Trump (after his most recent assault on Curiel) that he had no choice.

This captures the dilemma that many Republicans find themselves in. Many, like Kirk, backed Trump (to varying degrees) in spite of all of those positions and public statements. It’s worth noting that many of those were delivered during the GOP primaries, when the media scrutiny on Trump was a faint echo of what it is now becoming. With the general election beginning in earnest, the scrutiny is intensifying in a big way — primaries simply don’t come close to general elections in this regard, and there is just no telling how anyone will hold up under this level of brutal media pressure. Trump is not holding up well, and the reflected heat is suddenly a lot harder for his fellow Republicans to endure.

This means two things. First, if Trump continues to do wretched things like attacking judges based on their heritage, more Republicans might feel tempted to un-endorse, as Kirk did. And second, the general election audience is now beginning to tune in, and is paying closer attention to all of Trump’s previous controversial statements, which are now receiving much greater circulation in Democratic ads and messaging. Remember, the operating assumption for top Democrats is that, even if Trump has high name recognition due to his media ubiquity, many voters are not aware of the full specific range of wretched and depraved things he’s said and done over the past year. That will now change.

Thus, even if Republicans do un-endorse in the wake of any new Trump atrocity, Dems can still try to hold them accountable for having backed Trump despite all his previous public statements. And if they don’t un-endorse, Dems can try to hold them accountable for all those things and any fun new surprises that he springs on us in coming weeks.

In other words, it’s not clear how much it will matter whether Republicans do or don’t unendorse Trump. They’re stuck with him, and, whether or not he cleans himself up (which seems unlikely), he’s already left a year-long trail of wretchedness and depravity that Dems will now try to hang around their necks.