Rep. Ann Kirkpatrick (D-Ariz.) released an ad attacking Sen. John McCain (R-Ariz.) for supporting Republican presidential candidate Donald Trump. (Kirkpatrick for Senate/YouTube)

It's fair to say the above video is an ad that Democrats have dreamed of producing. But until recently, they probably didn't think they would get to.

In it, Rep. Ann Kirkpatrick (D-Ariz.) repeatedly ties Sen. John McCain (R-Ariz.), the Republicans' 2008 presidential nominee, to a leading Republican who has praised waterboarding, suggested banning Muslim immigrants and questioned McCain's own war hero background. McCain, as the ad points out, has repeatedly said he'll accept Donald Trump as the GOP nominee.

As recently as a year ago, a political attack ad like this would have been nearly unthinkable. But the political reality today is that Republicans' front-runner has said all those things and looks poised to capture the 2016 Republican nomination. If you're McCain and the eight or so Senate Republicans up for reelection in swingy or even blue-leaning states, this is more like a real-life nightmare.

Democrats challenging vulnerable Senate Republicans for their seats and, ultimately, for control of the Senate in November have plenty to work with when it comes to Trump's controversial, inflammatory, eyebrow-raising comments that often isolate whole sectors of general election populations in one fell swoop. Even Republicans have occasionally denounced the man who could soon lead their party when he's gone too far. And there's a reason for that: They were concerned his views would be cast as theirs. Well, now they have.

Any Republican who has repeated the establishment line that he or she will support whoever is the GOP nominee -- the argument here being a Republican would be better than Hillary Clinton or Bernie Sanders -- is subject to the brutal editing of Democratic ad-makers, the end result being like the ad we see here.

How effective this ad will be, of course, remains to be seen. A recent Washington Post-Univision poll suggested some voters are able to distinguish between a man like Trump and a man like McCain; more than 6 in 10 Hispanic voters said Trump’s views on immigration are not representative of the Republican Party overall, for example.

But it's not like the worst is over now that the nominating process could be coming to an end. As The Fix's Chris Cillizza wrote this weekend, at any moment, with the click of a Twitter button or a mic in his hand, the unpredictable Trump can drag the Republican Party into a controversy about the Ku Klux Klan or Benito Mussolini or something else equally uncomfortable for Republicans on the ballot and equally enticing for Democrats trying to unseat them.

In short, get ready to see a lot more ads like this one.