In every Washington Post/ABC News poll since July, Donald Trump has led the Republican field. In every poll since September, he's enjoyed the support of more than 30 percent of Republican voters. The newest poll, released on Tuesday, has him at 34 percent -- down slightly from late January and with his lead falling to 9 points.

This is only one poll, of course. At the same time that his support is slipping slightly in our poll, he's at a new high in the Real Clear Politics average of recent polls -- thanks mostly to the 49 percent he got in a recent survey from CNN/ORC.

What's happened in our poll since the end of January is not a secret: The field has gotten much, much smaller. That's why the three non-Trump lines on that first chart have all spiked upward: Candidates dropped out, and their supporters are now supporting someone else. Some voters may have had to switch candidates multiple times; it's hard to know.

This suggests, though, that Trump isn't adding much support as people drop out. Which leads us to the natural hypothetical: What if two more people drop out, and it's a one-on-one race?

We can assume that Trump won't drop out at this point, for obvious reasons, and we can assume that, of the other three, Kasich is the most likely to go (though Rubio's probably teetering, too). So what does a hypothetical Cruz-Trump or Rubio-Trump contest look like?

It looks like a nominee named Cruz or Rubio.

Well, sort of. This is a national poll, and as we are reminded every few days at this point, it's states that delegate the delegates.

What's particularly interesting is where the new support for Cruz and Rubio comes from. In four-candidate polling at this point, Trump leads Rubio by 2 points with women, but trails Cruz by 4 with that same group. If the field consolidates, though? Cruz gains 37 more points of support from women -- and Rubio gains 41. Across the board the picture is similar: Much more new support goes to the non-Trump than to the Trump.

Across demographics, Cruz gains 30 points on average once Rubio and Kasich are out; Trump gains 7.5 points. Trump gains about 11 points on average if the field is him versus Rubio -- but Rubio gains an average of 34.

Interesting, right? The obvious challenge for Cruz and Rubio is that we are not currently in a one-on-one race and that Trump already has a lead in the delegate count that, if recent history is a guide, may be hard to overtake.

In one week, the winner of Ohio will get 66 delegates and the winner of Florida 99 -- 5 and 8 percent of the total needed for the nomination, respectively. It seems likely that Cruz or Rubio could gain those 165 delegates if they were running against Trump one-on-one.

But, for now, they aren't.