President Obama strongly criticized Donald Trump's suitability for president during an August 2 news conference at the White House. (Reuters)

It's no secret that President Obama doesn't think much of Donald Trump. But on Tuesday Obama took his critique of the Republican presidential nominee up a notch, blasting Trump as "unfit" to serve during a joint news conference with the Singaporean prime minister at the White House.

“The notion that he would attack a Gold Star family that made such extraordinary sacrifices on behalf of our country, the fact that he doesn’t appear to have basic knowledge around critical issues in Europe, in the Middle East, in Asia, means that he is woefully unprepared to do this job,” Obama said.

That's a remarkable statement — both for the words Obama used and where he used them.

Let's take the second part first. This wasn't Obama speaking at the Democratic National Convention last week in Philadelphia or out on the campaign trail in support of Hillary Clinton's presidential bid. This was at the White House. And not just that. It was during a press event standing alongside a foreign leader. This was Obama as statesman and diplomat, the face of the United States to the world. That Obama would be willing to say what he said on such a stage is telling — and decidedly unusual.

Now, for what he actually said.

"Unfit to serve." "Woefully unprepared." "There has to come a point at which you say enough."

Those are very strong words. And Obama made sure everyone knew why he was using them: not because Trump is a Republican and he is a Democrat but because he had genuine worries about Trump sitting in the Oval Office. That makes his critique of Trump different in kind from simple partisan sniping.

"I think I was right and Mitt Romney and John McCain were wrong on certain policy issues, but I never thought that they couldn't do the job," Obama explained. "But that's not the situation here, and that's not just my opinion. That is the opinion of many prominent Republicans. There has to come a point at which you say enough. And the alternative is that the entire party, the Republican Party effectively endorses and validates the positions that are being articulated by Mr. Trump. And as I said in my speech last week, I don't think that actually represents the views of a whole lot of Republicans out there."

What's Obama up to with such a broadside against Trump?

Well, first off, he genuinely believes it. Obama has expressed his surprise-bordering-on-exasperation with the idea that a country that elected him as the first African American president eight years ago could put forward Trump as the Republican nominee in 2016. He views Trump as not only totally outside the mainstream of political thought — Democratic and Republican — in this country but as someone who could be dangerous to the country's welfare if he managed to win the White House.

There is, of course, a political calculation involved here too. Democrats — led by Obama and the Clintons — spent the entire last week at their convention in Philadelphia trying to decouple people's partisan feelings with their need to vote for Trump. Here's a key portion of Obama's convention speech:

We Democrats have always had plenty of differences with the Republican Party, and there’s nothing wrong with that. It’s precisely this contest of idea that pushes our country forward. (Applause.) But what we heard in Cleveland last week wasn’t particularly Republican — and it sure wasn’t conservative. What we heard was a deeply pessimistic vision of a country where we turn against each other, and turn away from the rest of the world. There were no serious solutions to pressing problems — just the fanning of resentment, and blame, and anger and hate.

The strategy here is simple: Cast Trump as something other than a conservative or a Republican and, in so doing, give "real" Republicans license to vote for Clinton.

Trump is helping that cause by repeatedly dismissing and/or threatening members of the leadership of his party. His latest was praising Speaker Paul Ryan's primary opponent for saying nice things about him.

What Obama and his party hope to do is fundamentally alter the governing political dynamic that has been in place since the 2000 election: 47 percent of people ALWAYS vote for the Democrat and 47 percent ALWAYS vote for the Republican. It's been a simple lining-up-behind-party-banners for a decade and a half.

But Obama and Clinton sense, rightly, a unique opportunity in Trump's candidacy. His loose affiliation with the GOP and its principles has led to an ongoing revolt against him by the Republican establishment and its voters. If Clinton can persuade even a quarter of those voters to throw off their partisan affiliation and cast a vote "for the good of the country," she could remake the deeply divided electoral map that has come to define our politics.

A year ago, I would have said that strategy was a total fantasy. Now, I think it has a real chance of working. Call it the Trump Effect.