A head to head comparison of the Georgia 2016 Primary gives us an idea of the break down of the voters.
Hillary Clinton received 22% (935 K votes) beating both Bernie Sanders by 11% (475 K votes) and Donald Trump by 3% (757 K votes) in the overall count of votes in California if the election were among these 3 candidates. Democrat race by this time was a 2 person race between Hillary & Bernie. However, Republican side, Donald had 2 strong contenders in Ted Cruz, Marco Rubio, while John Kasich & Ben Carson took around 3% to 3% of the vote.
Ted Cruz won 214 counties. Donald Trump wins 2 out of the 254 counties in the state of Texas to support his claims of his movement in the country. Bernie Sanders won 3 counties in the state of Texas. Hillary Clinton needed only 35 counties to beat Donald Trump in Texas, which could only mean she won big in some large population counties.
These 10 counties play an important role in these primary elections. Unlike in California, in Texas, top county though quite big is not an order of magnitude larger than the other counties. Even though a candidate, can get a sizable majority in a large county it is possible for the other candidate to catch up from the smaller counties.
Bernie Sanders vs Clinton
Hillary Clinton vs Donald Trump
Donald Trump vs Bernie Sanders
In a head to head match up on just the total number of votes, Hillary Clinton (66%) beats Bernie Sanders (34%). Hillary Clinton vs Donald Trump, she wins by 10 pts with an 42K vote difference where she had to compete with only one opponent and he with 4 more.
Hillary Clinton did extremely well in Harris & Dallas counties (almost twice the votes) when compared to Bernie Sanders and for Donald Trump. Bernie Sanders did well in Harris county but did not cross not hit the 25% (21% max) in any of the top 10 counties.
Ted Cruz and Marco Rubio did take a decent size of the vote count in majority of the top 10 counties in the state which took away from Donald Trump majority. John Kasich, Ben Carson each won under 5% of the votes in the top 10 counties.
Related References: 2016 Texas General Election Story, 2020 Texas Primary Election Story