Could both of our political parties lose their rationale for existence?

Jonah Goldberg writes in USA Today,

...“During Obama's eight years in office, the Democrats have lost more House, Senate, state legislative and governors seats than under any other president,” writes NPR’s Mara Liasson. She adds, "Democrats currently hold fewer elected offices nationwide than at any time since the 1920s."

There are many reasons for this, but one is particularly relevant. Obama lost the traditional heart of the Democratic Party: the white working class. In fairness, the Democrats’ trouble with blue-collar whites pre-dates Obama, but Obama accelerated the process. In 2012, he lost this group by 26 points (62%-36%). Trump is winning with those votes.

... Moderate and centrist Democrats have been effectively purged from the party. Hillary Clinton might look like a somewhat conservative Democrat to some, but that’s mostly because she has been hounded for months by an avowed democratic socialist.

If the GOP actually did implode tomorrow, it would spell both a short-term bonanza for the Democrats and a long-term existential crisis. People forget that beyond policy and philosophy, what sustains both parties is a kind of team sport. The Democrats run on being anti-GOP, and the Republicans campaign on being anti-Democrat. Take away one dance partner, and the one left on the floor has no idea what to do next.

And dancing with Donald Trump won't be anything like dancing with Ted Cruz, who has suspended his campaign. The Democrats have no idea how to tango with a new GOP that also promises to maintain or expand entitlement programs, raise trade barriers and tax the wealthy. If the Republican Party under Trump joins Democrats in wanting to fund Planned Parenthood, how will we tell who is leading and who is following?

Whether Trump destroys or merely transforms the GOP, the net effect could be the same: Both parties could lose their reliable rationale for existence. That kind of creative destruction could leave a vacuum for one or more new parties to fill the void.