Donald Trump got viciously personal in his attacks on Hillary Clinton

Real-estate tycoon Donald Trump raised eyebrows Monday night with some of his attacks against former Secretary of State Hillary Clinton.

Trump, the Republican presidential front-runner, used what some people interpreted to be a crude remark - "schlonged" - to describe Clinton's loss to then-Sen. Barack Obama in the 2008 Democratic primary.

"She was favored to win. And she got schlonged. She lost. I mean, she lost," Trump recalled, speaking at a rally in Grand Rapids, Michigan.

Trump was discussing Clinton's past White House bid while arguing that "everything that's been involved in Hillary has been losses," and pointing to last Saturday's Democratic presidential debate.

"Let's assume that Hillary becomes president - oh, my God. Oh, she'll be the worst. Is that a president? You saw her the other day, in all fairness. You saw it the other day. You saw the debates where they hide them between football games," Trump said. "Let me just tell you: I may win. I may not win. Hillary, that's not a president."

Trump added: "This is not a president. Now, you can say what you want. And we can be nice, or we don't have to be nice."

The two presidential front-runners have escalated their attacks on each other in recent days. Trump demanded an apology Monday for a supposedly "disgusting" debate claim, in which Clinton said the terror group ISIS was using videos of Trump to lure new recruits. The Clinton campaign refused the request.

During his Monday-night rally, Trump also repeatedly called Clinton "crooked," and before that he again brought up her debate performance. Trump highlighted an awkward moment in which the Democratic front-runner was briefly missing from the stage after a commercial break. According to reports, she was returning from the bathroom.

"I haven't started with Hillary yet. What happened to her? I'm watching the debate and she disappeared. Where did she go?! Where did she go?! I thought she quit! I thought she gave up! Where did she go? Where did Hillary go?" Trump asked. "They had to start the debate without her. Phase two. I know where she went. It's disgusting. I don't want to talk about it. No, it's too disgusting. Don't say it. It's disgusting."

As his audience laughed, Trump asked: "Wasn't that a weird deal?"