When Republican voters talk presidential politics these days, the conversation often steers to this question: "If it's Trump vs. Hillary, who do you vote for?"

It's a not-crazy question with a non-obvious answer for many in the GOP who might have a tough choice to make in November 2016. Despite all his supposed gaffes and heresies, Donald Trump continues to be the Republican Party's presidential frontrunner. He's dipped a bit from his peak popularity, but Trump still leads national polls with double and triple the support of more mainstream candidates such as Marco Rubio and Jeb Bush. Betting markets are more skeptical, but give Trump more than a slugger's shot. Primary Guide, which converts U.K. bookmaker data into election probabilities, gives Trump a 12 percent chance of winning the nomination, versus 28 percent for Bush and 26 percent for Rubio.

There is a real chance that Donald Trump could be the Republican presidential nominee. At the same time, however, there are lots of GOP voters who still find Trump flat-out unacceptable. Although his approval ratings hit 50 percent in a recent USA Today-Suffolk University poll, his 37 percent unfavorable ratings were still far higher than opponents such as Ben Carson (9 percent), Rubio (13 percent), and Carly Fiorina (17 percent).

It's a given that some Republicans would flee Donald and reluctantly back Hillary in a general election matchup. So here's the real question: Would enough Republicans find the idea of a President Trump so distasteful/laughable/frightening that they would help make Hillary Clinton the 45th president of the United States?

Very possibly. A Quinnipiac poll of this matchup found Clinton narrowly ahead of Trump, thanks in part to 10 percent of self-identified Republicans backing her. By contrast, only half as many Republicans would defect if Bush were the nominee — one reason Clinton loses by two points in that matchup.

"Republicans for Hillary" might be a phenomenon reminiscent of the 2008 election, when nine percent of GOP voters went for Barack Obama versus the six percent who picked John Kerry in 2004. Back then, however, it was probably more a case of GOP voters inspired by Obama. This time it would be GOP voters repulsed by Trump.

And who could blame them for putting aside Benghazi, the home-brew server, and the idea of Bill back in the White House? Forget momentarily Trump's disparaging remarks about women and Hispanics and instead focus on his policy proposals. His first big, unserious idea was to deport 11 million illegal immigrants and build a wall to keep them out. This monumental — and ugly — undertaking could cost some $400 billion to $600 billion over two decades. Raising taxes on hedge fund managers, as Trump proposes to do, wouldn't even cover a tiny fraction of those costs.

But it's Trump's ridiculous tax plan that could really nudge millions of Republicans to pull the lever for Clinton. An analysis by the Tax Foundation projected his proposal would lose $10 trillion in tax revenue over the next decade, even assuming much faster economic growth. Although Trump says he would balance the budget "relatively soon" if president, his massive tax cuts would increase the federal debt-to-GDP ratio by a whopping 70 percent, according to the Committee for a Responsible Federal Budget. Oh, and don't forget Trump wants to do zippo about the explosion in entitlement spending.

Now imagine a debt-averse Republican voter, one already put off by Trump's bluster, comparing that blueprint to Clinton's. Although she has not released a comprehensive plan, let's assume it would be something more or less like the last Obama budget. That would have raised about $1 trillion in taxes, including limiting tax breaks for the wealthy and business, and would have reduced projected deficits by nearly the same amount. Few Republican voters favor tax hikes, of course. But a trillion-dollar tax increase — even one that raises capital gains taxes — might look a whole lot smarter than a reckless, budget-busting $10 trillion tax cut when you are already $20 trillion in debt. As any good conservative knows, life is about trade-offs.

Some top Republicans have done their best to make the Trump plan sound reasonable, maybe just in case he's the nominee. Both the Heritage Foundation's Steve Moore and Grover Norquist of Americans for Tax Reform have praised it as pro-growth and Reaganesque. But it is neither. Rather, it makes a red-ink soaked mockery of Ronald Reagan's "supply-side economics" and the idea that small government is good for the economy. And if Hillary is lucky — and should Trump get the nomination — enough Republican voters will realize the joke is also on them.