It is not merely that. They win elections and they stay loyal to the party once elected. We hold our noses and vote for RINO POS's like McCain and Romney, only to have them betray us at every opportunity. You'd never the the GOP RINO party do something like pass Obamacare. A lot of 'Rats knew they'd lose their seats and did; but they stuck together and got the monstrosity passed. RINOs always chicken out because they "don't want to be blamed" for something. The 'Rats either have more courage or they get enough money from slush funds to buy their loyalty. RINOs fold like cheap suits.
The Democrats got betrayed too, so many they voted for said they would not vote for Nancy Pelosi for Speaker but they did in the end. I doubt it but hopefully they will remember that.
The Democrat politburo had to buy off several senators to pass Obamacare.
The New Louisiana Purchase, Jumpin Jim Jeffords...
Commie-crats win by vote harvesting. Illegal, dead, multivoter, box-stuffing, etc. Yes, blind party loyalty contributes; but their rabid opposition to voter ID reveals the “strength” of their “base.”