Donald Trump got into it with pretty much every other candidate at the Feb. 13 CBS News GOP debate. (Peter Stevenson/The Washington Post)

If Donald Trump, up by almost 20 points in the South Carolina polls, wanted one thing from Saturday’s GOP debate in Greenville, S.C., it was for everything to go smoothly. If he can keep that double-digit lead for another week, he’ll dominate a second-straight primary state and further cement his status as the Republican front-runner.

But when Donald Trump has a microphone, things tend not to go smoothly — for better or worse.

Trump came out firing at the debate, and he went after his favorite target first: Jeb Bush. First he targeted Bush’s family, starting with former president George W. Bush. When Jeb said his mother, former first lady Barbara Bush, is “the strongest woman” he knows, Trump replied, “She should be running.”

Trump also called Bush “weak” on immigration, and in the exchange that earned him the most boos of the night, said, “The World Trade Center came down during your brother’s reign. Remember that.”

Then it was Ted Cruz’s turn. Remember when Trump and Cruz were best buds? Yeah, not so much any more. Trump has been attacking Cruz for weeks now, but the attacks got even more direct when Trump called Cruz “the single biggest liar” during an exchange about abortion.

The candidates aren’t likely to be much nicer to each other in the week leading up to the South Carolina primary. The state has a history of rough-and-tumble politics, and the bitter exchanges at Saturday's debate underscore just how important the primary is to the GOP hopefuls left standing after Iowa and New Hampshire. And while some of the more fiery moments Saturday might appear unseemly — even rude — nothing has knocked Trump down so far.