It’s no exaggeration to say that the next six months will determine the viability of the Republican Party. The demographics of this country are changing. This will be the last presidential election cycle in which the G.O.P., in its current form, has even a shot at winning the White House. And so the large question Republicans must ask themselves is: Are we as a party willing to champion the new America that is inexorably rising around us, or are we the receding roar of an old America that is never coming back?

Within that large question the G.O.P. will have to face several other questions.

The first is: How is 21st-century America going to view outsiders? For Republicans in the Donald Trump camp, the metaphor is very clear: A wall. Outsiders are a threat and a wall will keep them out.

Republicans in the Jeb Bush camp have a very different metaphor. As Bush and his co-author Clint Bolick wrote in their book, “Immigration Wars,” “When immigration policy is working right it is like a hydroelectric dam: a sturdy wall whose valves allow torrents of water to pour through, creating massive amounts of dynamic energy.” Under this metaphor the outside world is not a threat; it’s a source of creativity, dynamism and perpetual renewal.

The second question Republicans have to ask is: Can the party see reality? The great Victorian critic John Ruskin once wrote: “The more I think of it I find this conclusion more impressed upon me — that the greatest thing a human soul ever does in this world is to see something, and tell what it saw in a plain way. Hundreds of people can talk for one who can think, but thousands can think for one who can see.”