Donald Trump Warns Third-Party Run Guarantees Democrats Win Front-runner says contested convention "would be very bad for the party."

 -- Fresh off his multi-state win Tuesday night, GOP front-runner Donald Trump today said a contested convention "would be very bad for the [Republican] party."

"Let me tell you, a third-party guarantees -- not 90 percent, or 99 percent -- 100 percent that your Democrats will win, probably Hillary," he told "Good Morning America."

"I guess it's Hillary; looks like it if she gets to the starting gate.

"But it guarantees."

Trump was asked about his potential Democratic opponent if Hillary Clinton does secure her party's nomination. "She would be a major embarrassment for the county," Trump told George Stephanopoulos.

When it comes to the upcoming Supreme Court nomination, Trump once again said the Senate should not give Obama's choice a hearing.

"I think the Republicans should do exactly what they're doing," Trump said. "I think they should wait until the next president and let the next president pick."

He also said the next Supreme Court nomination and confirmation could have a lasting effect on the country.

"Now you have four Supreme Court judgeships coming up and that would mean they would take over for 50 years, probably," Trump said. "This country will never be the same."