The "center" of American politics is not a fixed point, it shifts over time. What is "the center" today would have been considered pretty far left in the 1990s. Likewise, what was the imagined "center" in the mid-1980s would have been considered pretty far right in the 70s.
One of Lincoln's skills as a politician was that he moved the center of American politics into an antislavery place, and he also evolved in his own thinking about slavery and race. Finding and helping to move "the center" is one (not the only) form of effective politics.
There is no such thing as a democratic political culture that lacks an imagined "center" and people who inhabit it. This is especially the case in a diverse and often fractious nation. The politics of persuasion is all about moving that imagined center in the direction you want.
Most of the people currently on the American far right are highly unlikely to move to the center, because their basic political commitments are hostile to America's multi-racial democracy. One task ahead is to prevent that segment of our political culture from growing.
How to do that is unclear. History shows that deplatforming can often work. History also shows that sometimes right wing radicals can gain fame and attention by presenting themselves as "martyrs" who've been persecuted by "elites." There's no iron clad formula.
Donald Trump gave new energy and focus to an American far right that has existed in its modern form for over 100 years. It has ebbed and flowed in numbers, and shifted in its focus. But it's always been with us, and likely always will.
The question as I see it, looking ahead, is what the relationship between the GOP and the far right is going to be. In US politics, parties are incredibly important. Get the GOP nomination, and you basically inherit ~50 million voters w/o doing a thing.
In 1964 Barry Goldwater's nomination was seen as a victory by the American far right, a step toward taking over the GOP. Reagan's 1980 victory was seen as the next step in that process. The war within the GOP has waged for over 50 years, but 2016 was a tipping point.
If the GOP finally completes the process of pushing anyone who is not 100% on board with Trump's far right politics out of the party I think the 2 most likely outcomes would be....
1) the party becomes electorally unviable and fades away. 2) the party wins an election and its illiberalism becomes the new center as it stamps its anti-democratic agenda upon the nation's institutional structures (voting, immigration, education, labor policy, etc.)
Because we live in such a highly mediated political culture where digital information streams have more power to shape people's views of the world than face-to-face relationships, how media and political elites on "the right" comport themselves in the next few years will be key.
If this continues to be the approach on Fox and on Facebook, then the chances of a non-far right GOP emerging will be much decreased. https://www.mcclatchydc.com/news/politics-government/article128160654.html
At this point, I have the tiniest imaginable iota of faith in the likelihood of any media outlet on the right evincing even the slightest shred of integrity and reasonableness. I base that on their historical track record. But sometimes historical patterns change.
One final thought. In a democratic political culture, you can't just lock up people you disagree with (unless they commit crimes) and you can't change all of their minds. But what you can do is deprive them of political power by defeating them soundly in elections.
And you win elections by giving voters a reason to vote for you, like by delivering policies that positively impact people's lives and enable them to live lives of dignity and self-determination.