(CNN) President Donald Trump has become more popular since the election. As I wrote last month , his net favorability rating has climbed by more than 8 percentage points since he before the 2016 election. A closer examination of his polling reveals why he's become more popular: It's almost all about the demise of the anti-Trump Republican.

Before Trump won the 2016 election, we heard a lot about Republicans who didn't like him. Many Republican officials refused to endorse Trump . Even House Speaker Paul Ryan was slow to endorse him

The polling bares Trump's previous problem with Republicans. His net favorability rating among Republicans in an average of surveys from CNN, Fox News, Marist College, Quinnipiac University and Suffolk University was only +50 percentage points.

That may seem high, but consider that Mitt Romney's net favorability rating among Republicans was +95 percentage points among Republicans in CNN's final poll before the 2012 election. In other words, Romney was about twice as popular with Republicans as Trump.

Trump benefited, though, from having Hillary Clinton as his opponent. In the end, he got many people who disliked him to vote for him and was able to carry Republican voters by 80 percentage points

Since the election, Republican officials have had a different attitude toward Trump. We've seen many cow to him, and they have defended him at most turns. Those who have been most antagonistic toward Trump, like Sens. Bob Corker of Tennessee and Jeff Flake of Arizona, have decided to call it quits before having to face the electorate.

A large reason why Republicans have been unwilling to speak out like they did before the election is that far more members of the Republican electorate now like Trump. That is, it's electorally dangerous to go against him.

His net favorability with self-identified Republicans among the five aforementioned pollsters stands at +71 points. That's good enough for a 21-point jump from before the election. Put another way, his unfavorable rating before the election stood at 23% among Republicans. It's now down to just 12%, which is a very small part of the party and about equal to the percentage of Democrats who viewed then-President Barack Obama unfavorably in a CNN poll at a comparable point in the Obama presidency.

What isn't clear is who the Republicans are who now view Trump favorably and didn't before. There are, no doubt, some Republicans who didn't like Trump before and now do. There are also probably some people who didn't identify as Republicans prior to Trump's election who now identify as such because they like him. Also, there are probably some Trump haters who previously identified as Republicans but don't now because of him.

Either way, Trump is reshaping the Republican electorate in his image. A far larger share of Republicans than before the election now don't just tolerate Trump but actually like him. One could say the Republican Party is now Trump's party.

What the President doesn't seem to be doing is upending the electorate at large. Even as far more Republicans like Trump, that's not really the case among Democrats and independents. His net favorability among both is up somewhat, though not by anywhere near the same level as among Republicans.

His net favorability with Democrats has risen slightly from -89 percentage points to -83. His net favorability among independents is up from -29 percentage points before the election to -26 now.

The lack of large improvement among Democrats and independent identifiers is interesting and potentially troublesome for the President. It means Trump has really gained significant ground only among those people (Republicans) who were most favorably disposed to him and voted for him even when they didn't really like him. Soon enough he will run out of Republican voters to like him who didn't previously.

For Trump to continue to see an uptick in his popularity, he'll eventually need to start convincing far more people who aren't Republicans to like him. Convincing Democrats and independents to be pro-Trump is far different from getting Republicans on his side. It may also be more difficult considering that not very many of them have changed their opinions of him since the election.