It will apparently be on the 442nd day of Donald Trump's presidential campaign, during a speech Wednesday in Arizona, that the Republican nominee will finally outline his detailed policy plans on his campaign's signature issue, immigration.

Over the course of the week, political reporters and linguists have tracked on the map where Trump's position seemed to be (or at least seems to be headed). Trump told Fox News' Sean Hannity on Wednesday that he was open to softening his previous insistence on deporting every immigrant here illegally; on Thursday, he told CNN's Anderson Cooper that, actually, it was more of a hardening.

Regardless of the shift in the density of his position, Trump has made clear overtures toward a position that is less strident than what he offered during the Republican primary, including, potentially, a system by which immigrants here illegally might eventually be allowed to stay.

We won't know precisely that his proposal is until next week, it seems, but we can talk right now about why such a change is being considered at all.

On Thursday, Pew Research released polling showing that there's a wide partisan split on views of how to deal with illegal immigration. About a quarter of the population would emphasize increased border security and enforcement of immigration laws; another quarter would rather see a path to citizenship for those here illegally. About half the country thinks that both should be prioritized. When forced to pick, more lean toward citizenship.

But that differs strongly along party lines.

Of course, that's why Trump's pitch worked in the primary: He was saying what a lot of Republicans wanted to hear.

The problem for Trump in the general election has been that he hasn't figured out how to expand the base of support he enjoyed in the primary. He's been stuck in the low-40s in polling for months, with rare exception. After the party conventions, Democrat Hillary Clinton took a big lead, thanks in part to softness from Republicans -- which itself was partly sparked by skepticism from college-educated voters and women.

When The Washington Post and our polling partners at ABC asked voters how they felt about Trump's immigration proposals in September -- which it's safe to assume most understood as being pretty far to the right and centering on building a wall -- perceptions were split. Most importantly, college-educated whites viewed Trump's ideas less favorably than did non-college-educated whites, just as the former group now views Trump less favorably than the latter.

In July, we asked voters if they wanted a president who supported a path to citizenship. Among Republicans, 21 percent of those who supported a path planned to vote for Hillary Clinton. Two-thirds planned to vote for Trump. That's the gap that Trump is trying to close.

Won't he pay a political price? Maybe not as much of one as you might think. The Pew data forced people to choose between strict measures and more lenient ones. In July, Gallup asked people how they viewed these issues independently. Among all voters and all racial demographic groups, a path to citizenship was viewed favorably. The number among white Americans was 84 percent, with 40 percent of white Americans strongly favoring a path to citizenship. That suggests that many of those who like Trump for his hard-line rhetoric are more receptive to a citizenship pathway than it might at first seem.

The core of the question, then, is if this latest Trump move (if it happens!) will actually break down some of the resistance that he sees from his base. That's a harder question to answer. They'll be asked to decide if they think that the Donald Trump who was being sincere was the one they saw in the first 442 days of his campaign, or the one that emerges in the last 69.