Donald Trump is firing warning shots at the national Republican Party

Property magnate Donald Trump fired a warning shot at the national Republican Party on Monday.

The GOP presidential front-runner tweeted that the Republican National Committee was reportedly "getting ready to treat me unfairly - big spending planned against me."

"That wasn't the deal!" Trump exclaimed.

The "deal" was an apparent reference to the pledge Trump signed in September to not launch an independent presidential campaign should he lose the nomination.

At the time, Trump said that he was happy to sign the nonbinding pledge because the RNC assured him that it would treat him "fairly."

But Trump's tweet on Monday suggested that he could be trying to use a third-party run as leverage against the RNC again.

He also hinted at the possibility the day before during an interview on ABC's "This Week." Host George Stephanopoulos asked Trump about a recent Wall Street Journal report on a supposed "guerrilla campaign" being planned against him.

He asked if that could lead to Trump rethinking his third-party pledge.

"Well, we'll see what happens," Trump replied, according to ABC's transcript. "It will be very interesting. But I'm leading every poll by a lot. It's not even a little bit anymore, it's a lot."

Stephanopoulos pressed Trump again.

"Well, I'm going to have to see what happens," the candidate repeated. "I will see what happens. I have to be treated fairly. You know, when I did this, I said I have to be treated fairly. If I'm treated fairly, I'm fine."

It's not clear whether the "guerrilla campaign" will ultimately amount to a significant spending effort against Trump. That campaign is reportedly being spearheaded by Liz Mair, a former RNC online-communications director.

On Saturday morning, Trump and Mair also exchanged shots on Twitter: