Republican Sen. Rand Paul criticized Republican Sen.-elect Mitt Romney on Wednesday for writing an anti-Trump op-ed in the Washington Post.

In a press call, Paul suggested that the 2012 GOP presidential candidate may be experiencing “sour grapes” against Trump because Romney was not able to achieve the presidency after multiple attempts.

“It may be sour grapes not having won the presidency himself,” Paul told reporters on the press call when asked about Romney lashing out at Trump after accepting multiple endorsements from Trump in his political career.

Romney lost in a lopsided race in 2012 to President Obama.

Paul continued, saying he also believes “it’s virtue signaling. ‘Look at me, how virtuous I am.'”

Paul went on to say that the op-ed, “does not serve a useful purpose,” adding, “It’s Not useful. Not good for the country. Not good for the Republican party. I hope this will be a one-off.”

When asked if Romney had intentions to run in 2020, Paul remarked that Trump’s election victory was “extraordinary” and that a “run-of-the-mill establishment Republican” could never have won in 2016. Paul himself ran in 2016 and sparred often with then-candidate Trump.

“I don’t think there is an appetite for a Romney run inside the Republican Party, nor do I think that the Romney-type establishment, big-government Republican is frankly popular enough to win a general election,” Paul said bluntly.

Paul concluded by saying that Romney had ruffled feathers in the GOP Senate caucus and was “getting things off on a wrong foot” by writing the op-ed critical of the party’s leader.

“To a great degree, a presidency shapes the public character of the nation. A president should unite us and inspire us to follow ‘our better angels,'” Romney wrote in the piece published Tuesday, adding, “and it is in this province where the incumbent’s shortfall has been most glaring.” (RELATED: Mitt Romney Writes Anti-Trump Op-Ed, Questions Trump’s Character)

Paul came out swinging against Romney earlier in the day, comparing him to Republicans who attacked Reagan when it was popular.

“Like other Big Government Republicans who never liked Reagan, Mitt Romney wants to signal how virtuous he is in comparison to the President,” Paul tweeted, “Well, I’m most concerned and pleased with the actual conservative reform agenda @realDonaldTrump has achieved.”

Like other Big Government Republicans who never liked Reagan, Mitt Romney wants to signal how virtuous he is in comparison to the President. Well, I’m most concerned and pleased with the actual conservative reform agenda @realDonaldTrump has achieved.

https://t.co/vNvp2ZwyK7 — Senator Rand Paul (@RandPaul) January 2, 2019

Romney’s op-ed also drew the ire of Republican Party Chairwoman Ronna McDaniel, who is Mitt Romney’s niece. McDaniel tweeted, “POTUS is attacked and obstructed by the MSM media and Democrats 24/7. For an incoming Republican freshman senator to attack @realdonaldtrump as their first act feeds into what the Democrats and media want and is disappointing and unproductive.”

POTUS is attacked and obstructed by the MSM media and Democrats 24/7. For an incoming Republican freshman senator to attack @realdonaldtrump as their first act feeds into what the Democrats and media want and is disappointing and unproductive. https://t.co/ArhI7Bi7bo — Ronna McDaniel (@GOPChairwoman) January 2, 2019

Trump endorsed Romney for his Senate race and his presidential run in 2012. Romney sought a cabinet position in the early Trump administration but was not selected for the position.