“There is no political issue today that generates that kind of passion.”
No, there isn’t. But it need not always be one issue. It can be several. There are plenty of popular positions that remain largely untouched by Republicans, most importantly enforcement of immigration laws.
The trouble with saying “it can be several” is that the number of people who feel passionately in the same way about several issues is much smaller than the number of people who feel passionately about one issue.
At some point the math works against you.