There is a belief going around that Donald Trump changed the Republican Party. This is especially popular among the few moderates left in that party. They would like you to believe that after Trump is gone, the GOP will return to normalcy and work in a bipartisan fashion again (like it did several decades ago). There's only one thing wrong with that idea -- it is just NOT TRUE!
The party has not been bipartisan for years now. During the term of President Obama, the Republicans opposed everything he tried to do -- even when he moderated his agenda in the hopes they would compromise. They were even honest about it. Some of the moderates were honest enough to admit the party's congressional delegation met after Obama's election and decided to oppose anything he tried to do, whether it was good for the country or not.
Trump did not create the partisanship of the GOP. He just recognized it and used it.
The same was true of race. The GOP had a large part of its base that was racist and white supremacist. Back in the 60's, millions of racists abandoned the Democratic Party after President Johnson pushed three civil rights bill through Congress and signed them. The Republican Party welcomed those racists with open arms, giving them a majority in the South (something they had never had). Party leaders may have thought they could control the racists after admitting them, but they were unable to do that. And the party became a comfortable home for racists and white supremacists.
Trump did not create the racism in the GOP. He just recognized it and used it.
The same is true of misogyny and homophobia. Thanks to the inclusion of the white evangelicals in the party, it has long been anti-woman and anti-LGBT. Republicans consider women second class citizens, and won't even let them control their own bodies. Republicans also opposed giving the LGBT community the same rights that other Americans enjoyed (including the ability to marry the person they loved).
Trump did not create the GOP's misogyny and homophobia. He just recognized it and used it.
Trump was also very anti-immigrant while campaigning and serving in office. But he didn't create that either. The GOP was anti-immigrant long before Trump. The GOP killed several attempts to reform our immigration laws long before Trump became a politician. In fact, Trump used many immigrants in his businesses. But he changed when he decided to run as a Republican.
Trump did not create the GOP's anti-immigrant fervor. He just recognized it and used it.
The Republican Party had a dark and ugly core in its base. That had been true for a long time. And it's why Trump decided to run as a Republican. Although he was a moderate Democrat for most of his life, Trump knew he could not win a Democratic nomination. But he saw the ugliness in the Republican base, and he knew he could use that to make himself popular among Republicans. And he had the lack of character and morals to do that.
The Republican Party will not return to a bipartisan "normalcy" when Trump is gone. The racists, misogynists, homophobic, and immigrant haters will still be there, and they will still make up the majority of the party's base. Having Trump appeal to their base instincts has emboldened them -- and they are not going to be quite or go away.
The Republican Party is the party of hate. That's not going to change anytime soon.