[tanknetter]

If so, it wouldn’t matter so much if the Dem has 29%, because in the run-off all the R votes would coalesce. Right, or not?

Yes, exactly that.

Last year's US Senate election Mary Landrieu got 42% of the vote to Bill Cassidy's 40%. Meaning that Landrieu "won" the ... open primary.

In the general election, Landrieu got 44% and Cassidy got 56%.

[tanknetter]

Duh, sorry, I meant open general election and runoff, respectively.