Republican presidential candidate Donald Trump rolled to big wins in Michigan and Mississippi on Tuesday, brushing off a week of withering attacks from the party's establishment to solidify his front-runner status as four states voted in nominating contests. (Reuters)

Donald Trump is hardly the picture of a candidate who appeals to Southerners, and his ties to Christian conservatives in the region are hard to explain, at best.

And yet, the Manhattan businessman pulled off something just two other Republicans have done in the modern era — winning every state in the Deep South in a competitive primary. The last two who did it? George W. Bush and Ronald Reagan.

Trump's easy win in Mississippi on Tuesday completes the sweep of the five states that have traditionally comprised the definition of the Deep South — Louisiana, Mississippi, Alabama, Georgia and South Carolina. The other two who did it — Bush and Reagan —hailed from Texas and California, respectively. Both, of course, went on to become president.

And Trump did it with relative ease — despite facing another Texan in Sen. Ted Cruz. He won 4 of the 5 states by double digits and survived a close call in Louisiana on Saturday.

Sweeping the Deep South is more common among Democrats. Hillary Clinton just accomplished it in 2016 on Tuesday, after Barack Obama beat her in all five states of those states in 2008. Al Gore did it in 2000, though he won every state in the country over Bill Bradley that year. And Bill Clinton did it in 1992. And Jesse Jackson did it in 1988.

If nothing else, Trump's sweep of the Deep South proves that his appeal is difficult to pigeonhole or diminish. The bad news for him: The South is just about done voting. Now we see how much his appeal translates to other parts of the country, like the Rust Belt and the West.

Easily winning Michigan on Tuesday would suggest that he remains on the right track.