Is Trump hurting Republicans' long time prospect?

[Wiz in Wis]

No, I actually don't think so. Both parties in the US shift so there is an equilibrium between them and they both always represent ~50% of the electorate. It's obvious that Trumpism even in 2016 is already incapable of winning an election without both the Electoral College and a strong leftist third party to bolster them, and that its reliance on older voters (both in the general election and in the Republican primary, incidentally) means that it can't hope to survive for long. When it is decisively defeated (and this is a matter of when, not if, unless the people turning 18 now become very staunch advocates, which seems unlikely demographically), the Republicans will go through a period of figuring things out, but they'll be back.

Trump is helping the Republicans' long-time prospect enormously by taking actions to reduce Democrat immigration. Immigration is the single largest long-term threat to the GOP.

It's a little late on this front, don't you think? Decades late, in fact.

I think he thinks immigration rates are still like the 90s/00s. Clearly, they are not.

[Wiz in Wis]

No, I actually don't think so. Both parties in the US shift so there is an equilibrium between them and they both always represent ~50% of the electorate. It's obvious that Trumpism even in 2016 is already incapable of winning an election without both the Electoral College and a strong leftist third party to bolster them, and that its reliance on older voters (both in the general election and in the Republican primary, incidentally) means that it can't hope to survive for long. When it is decisively defeated (and this is a matter of when, not if, unless the people turning 18 now become very staunch advocates, which seems unlikely demographically), the Republicans will go through a period of figuring things out, but they'll be back.

Trump is helping the Republicans' long-time prospect enormously by taking actions to reduce Democrat immigration. Immigration is the single largest long-term threat to the GOP.

It's a little late on this front, don't you think? Decades late, in fact.

-I don't think there's any necessary equilibrium between the parties. Party dominance is effectively random, and there's no necessity for them to represent nearly 50% of the electorate. Remember the fourth party system, when, by random chance, except in the 1910s, the GOP was dominant on every level all the time.

Gary Johnson is a "strong leftist"

Why can't the GOP become the Party of the Elderly, like the Democrats are the Black Party?

Trump was benefited by older voters in the GOP primary, but was not dependent on them, in any case. Look at the New Hampshire exit polls.

I think you're missing a potentially fatal flaw here.