President Trump took a swipe at Sen. Mitt Romney after he criticized the president for allegations about a recent phone call with Ukrainian President Volodymyr Zelensky.

Trump’s Monday night tweet was a jab at the Utah Republican, which included video clips contrasting Romney's electoral defeat in 2012 to the president's victory in 2016.

According to a whistleblower’s claim, Trump pressured Zelensky to investigate former Vice President Joe Biden over his alleged involvement in the business dealings of his son Hunter in Ukraine.

Romney tweeted in part Sunday it would “be troubling in the extreme" if the whistleblower's allegation turned out to be true.

Regarding whether his tweet about Trump was expressing suspicion toward the president, Romney told the Washington Examiner, “My initial comment was pointing out something which I think is quite evident, which is what was being alleged in the media was very serious nature.”

“It should be considered seriously and, therefore, unusual steps should be taken including releasing the transcript and learning from the whistleblower what prompted his or her communication,” Romney continued.

When pressed about the developments claiming the whistleblower’s information came from a second-hand source, Romney said, “Let's get the facts, and then we can decide how to proceed at that stage, but right now all we have is conjecture and various sources that are unnamed. So let's get the facts out.”

Romney and Trump have not hidden their mutual antipathy. Trump has repeatedly criticized Romney for having lost an election that Trump thinks should have been easily won, and Romney revealed this month that he will not be endorsing Trump or any other candidate in 2020.