A March poll from Southern Media & Opinion Research put Mr. Jindal’s approval rating at just 38 percent, against 60 percent disapproval. His numbers had been similarly poor in a February survey by Public Policy Polling.

Some national political commentators are treating the news as being self-evidently injurious to Mr. Jindal’s chances of capturing the Republican presidential nomination in 2016. Obviously, Mr. Jindal has plenty of time to turn around his image in Louisiana. But if he doesn’t, would Republicans really consider nominating someone who is so deeply unpopular among his own constituents?

Actually, you don’t have to go back very far to find a precedent for when Republicans did exactly that. Their nominee last year, Mitt Romney, was very unpopular among Massachusetts voters by the time he finished his single term as governor in 2006.

The chart below tracks Mr. Romney’s approval and favorability ratings during his term, based on data from PollingReport.com. …

There are differences, of course, between Mr. Romney’s standing and Mr. Jindal’s — notably that it is much more difficult for a Republican to be popular in Massachusetts than in Louisiana. Nevertheless, this ought to demonstrate that having strong approval ratings in one’s home state is not a prerequisite for gaining the presidential nomination.