Win or lose, Donald Trump's performance in exploiting the power vacuum in the Republican party, amassing a following without preaching GOP orthodoxy, and giving Clinton and the Democrats a run for their money, has the potential to alter the political landscape for both major parties.
The GOP, for example, had staked its future on returning to the past; it steadfastly refused to accept changes taking place in our society, but took refuge in a fantasy universe where changes in the fabic of civilization could be not only blocked, but reversed. The party was foundering, consistently losing the popular vote in recent elections, and clueless as to how to alter that. Yet when Republican politicians look themselves in the mirror, this is not the image they see.
So it's quite possible that if Trump loses, they will claim his loss as justification for their own brand of regressivism. After all, he didn't spout a strictly Republican party line, and he lost. It's also possible they would misread a Trump win in the same way, but the real message for Republicans, win or lose, should be a wake-up call for change. Trump's peculiar brand of Republicanism may not be good for the country, but it could at least serve as a catalyst to modernize the party's message. At the very least, I would expect to see a lot of prominent, senior Republicans retiring from politics after a Trump win.
The Democrats, too, risk reading the election wrongly. If they read a Trump loss as a resounding victory for themselves, they will be deluded. Democrats need to realize that currently, neither party is looked on with much favor by voters, especially not by the youngest political generation. If a Trump win sets Clinton on the road to accelerated progressivism, she can count (most likely) on more gridlock, or if not that, possibly further growth of the bloc that went for Trump this time.
To me, overreach presents the biggest problem for both parties. Republicans have already succumbed to it - backwards! - as winners, definitely, rolling back major legislation and shifting our attitudes on multiculturalism back to where they were in Eisenhower's time. But even as they are casting themselves as losers, they assert that the election process must have been rigged (Trump), Clinton emails are a serious problem to be pursued endlessly (Chaffetz), and no Supreme Court justice will be successfully nominated by Clinton (Cruz). A Clinton win risks Democratic overreach; in this respect, the recent stories that Bernie Sanders is ready to start cashing in his socialist chips, as soon as Hillary is in the White House, is particularly disturbing.
Thanks largely to a guy named Newt, we no longer have the consensus on basics that has been the bedrock of our two-party system. I hope the winning candidate/party will dedicate his/their efforts to restoring it. The party that does so is likely to be the true winner in coming decades.