Announcing his presidential candidacy in Miami on Monday, Jeb Bush staked out the pro-immigration end of Republican politics. He spoke pointedly in Spanish and responded to pro-immigration protesters by promising to pass "meaningful immigration reform." (He has danced between offering undocumented immigrants in the U.S. a path to citizenship or a path to legalization.)

Announcing his presidential candidacy Wednesday in New York, Donald Trump staked out the other end of the spectrum. He promised to build a "great wall" along the southern border of the U.S. because he's a builder. And he vowed to make Mexico pay for it because he's Donald Trump.

The rest of the Republican field is arrayed along the Bush- Trump continuum, with Florida Sen. Marco Rubio closer to Bush and Wisconsin Gov. Scott Walker nearer to Trump — for now.

We don't know which Republican will be the nominee. But barring a Democratic catastrophe, I bet the nominee ends up a lot closer to Bush's end than to Trump's.In fact, the 2016 Republican nominee will almost certainly promise to legalize many of the roughly 11 million undocumented immigrants in the U.S. (albeit not by executive action).

Why?

Hillary Clinton faces many obstacles, not least that it's difficult for a party to win the White House in three consecutive elections. But if she manages to reconstitute the Obama electorate (and right now, who's stopping her?), she'll win. If she adds a few more white women to the mix (and right now, who's stopping her?), she'll win with a thump. The closer Republican regulars get to Election Day without altering that trajectory, the more they'll be willing to concede, rhetorically at least, to avoid a loss.

Citizenship — or at least legalization — for undocumented immigrants who've lived in the U.S. for a long time (as most have) is powerfully symbolic, which is why it's such an important threshold. A party free from Republicans' history of racial politics might get the benefit of the doubt about its motives. Republicans don't. Their opposition to undocumented immigrants is too readily equated with a refusal to accept 21st century America at face value. Fifteen years into the new century, with demographics changing rapidly, that's increasingly untenable.

As Bush said at a National Review event in April, "We're gonna turn people into Republicans if we're much more aspirational in our message, and I think our tone has to be more inclusive as well."

The opposite is also true: They're going to turn people into Democrats if they don't make the changes that Bush champions. (Imagine how the seedy "debate" over Obama's birth certificate, indulged at the highest levels of the Republican Party, played out among recent Asian and Hispanic immigrants who view their own children's U.S. birth certificates as precious assets.) A Washington Post article today makes the point that Republicans won't win minority votes until they adopt policies that minorities support. The more serious danger is that minorities are endorsing liberal policies because they increasingly identify as Democratic partisans. A small case study: In 2012, support for same-sex marriage among blacks — the party base — jumped from around 41 percent to 59 percent in a Washington Post/ABC News poll taken after Obama spoke out in favor of it.

Supporting legalization in the fall of 2016 won't eliminate the GOP's reputational burden. But a softer tone and more inclusive proposal — speaking more like Bush or Ohio Governor John Kasich — could make the prospect of a Republican in the White House less threatening to millions of occasional Democratic voters who may or may not get to the polls. (Meanwhile, Republican base voters will still turn out for a squishy Republican if the alternative is a detested Democrat.)

In the primaries, Republicans may grow more restrictionist on immigration, with debates marked by Trumpian descents into disrespectful rhetoric. In a January Gallup survey, more than four of five Republicans said that they were dissatisfied with current immigration levels — a double-digit increase over a 2014 Gallup poll. But the rhetorical dodge of first promising to "secure the border" — whatever that means — will give the eventual GOP nominee leeway to propose legalization as a reward for achieving that mythical level of security.

In Politico yesterday, former Romney deputy campaign manager Katie Packer Gage wrote that polling and focus groups done by her consulting firm indicate that hard-core anti- immigrant views alienate "critical general election constituencies."

Furthermore, 53 percent of general election voters from key swing states would be less likely to vote for a candidate they viewed as anti-immigration. That dwarfs the 29 percent of likely general election voters who would be more likely to vote for an anti-immigration candidate.

That kind of data should set the tone for Republicans in the months before Election Day. Whether any president — Democrat or Republican — can actually deliver legalization, let alone citizenship, is another matter. House Republicans have repeatedly thwarted efforts to ease the plight of undocumented immigrants, opting instead to put the American dream further out of reach. Perhaps House Republicans will begin to care enough about presidential politics to alter their stands after 2016. But it's not at all clear that they will.