As recent as the 1960s, in many states, there were few primary elections, and many candidates of parties were chosen by political insiders at caucuses. That is why Bobby Kennedy actually had little chance of beating Hubert Humphrey in 1968, if Bobby had lived.
People need to keep in mind how Cuccinelli was able to get the Republican nomination for Governor. There was no Republican primary. Cuccinelli maneuvered to have the primary killed. Instead, he was selected by party insiders who serve as delegates at a party convention.
Once Lt. Governor Bolling realized there would not be a primary, he pulled out of the race, which left Cucci as the sole candidate. Bolling had a great deal of support from mainstream Republicans, but it was not enough.
Excerpt from the linked opinion piece in the Post:
"Limiting voter participation in elections is anti-democratic; itís also frequently self-defeating. Republicans in a number of states, including Virginia, tried to obstruct voting by minorities, the young and the old by means of tougher voter ID rules in this yearís presidential elections. It didnít work. But it certainly reinforced the impression that Republicans are hostile to those voters.
... practicing exclusionary politics, as Mr. Cuccinelli has done in blocking a party primary, is likely only to leave a residue of resentment."