Sen. Ted Cruz (R-Tex.), left, speaks with fellow presidential contender Donald Trump. (Pete Marovich/Bloomberg News)

Let's say that there were a national election for the presidency, everyone voting at the same time, and everyone were voting tomorrow.

Let's say further that Jeb Bush and Marco Rubio and Chris Christie and John Kasich all decide to put their differences aside and all agree to have their combined support go toward one unified establishment candidate, voting laws be damned.

If they did so, according to a new poll from NBC News and the Wall Street Journal, the effect would not exactly be what they were hoping for. That unified candidate would still come in second to Donald Trump, earning 26 percent of the vote to Trump's 33. Ted Cruz would come in third with 20.

There's a bit of data from that poll that reveals how dramatically the race has shifted over the past six months. In June, 75 percent of Republicans could see themselves coming around to vote for Bush, while only 32 percent said that about Trump. Now? Nearly two-thirds of Republicans would consider backing Trump — and only 42 percent would consider Bush.

But Trump's numbers aren't quite as good as Cruz's in that regard. If there's going to be a candidate around whom the party can coalesce, 71 percent of Republicans said they'd think about backing Cruz.

If you think about it, if you squint really hard, Cruz could be seen as an establishment candidate, too. I mean, the guy worked in the George W. Bush administration. He's a sitting senator, for Pete's sake — not a super-popular one, but representing 1 percent of half of the legislative branch isn't exactly outsider status. Clearly there are a number of non-Cruz voters who might think about voting for him.

NBC and the Wall Street Journal asked about another theoretical election-day-is-tomorrow scenario. Let's say that, in a desperate attempt to keep Trump from being the party's nominee, everyone else — Ben Carson, Carly Fiorina, Rand Paul — agreed to drop out. Even Jim Gilmore picks up the phone to tell his supporter that he won't be running. Instead, it's a two-man race, Trump vs. Cruz, for all the marbles. The result? Cruz wins, 51 to 45.

What's remarkable about this is that if you picked Rubio to be the sole opponent, he would still lose to Trump by seven points. If you had it Trump vs. Cruz vs. Rubio, Trump wins that, too, by nine points.

Only in Trump vs. Cruz, mano-a-mano, does Trump get taken out. The Canadian-born David vs. the skyscraper Goliath.

In a contest that doesn't and won't exist. In Iowa, Cruz is already close to beating Trump. A week later, who knows what might happen in New Hampshire. Cruz might beat Trump the old-fashioned way — state by state by state. Or someone else might beat both of them.

If there's a sudden shift to an election tomorrow, though, the Republican establishment will be caught between a rock and a hard place. It's this that has big donors waking up at night, screaming.

Donald Trump and Ted Cruz avoided going after each other on the debate stage or the campaign trail – until this week. The Fix's Chris Cillizza explains why the Trump-Cruz dynamic isn't going away any time soon. (Peter Stevenson/The Washington Post)