Hillary Clinton
NBC anchor Joe Scarborough suggested Hillary Clinton 'smile' following her victories on Mega Tuesday.Getty Images

"Smile. You just had a big night. #PrimaryDay" With just one tweet directed at Democratic frontrunner Hillary Clinton, NBC's Morning Joe host Joe Scarborough found himself in hot water. The outspoken Republican news anchor's comment was met with scathing accusations of sexism and even spurred a hashtag: #SmileForJoe.

Scarborough was initially met with replies deriding him for suggesting the only remaining woman in the race should smile following her victories across four states. "@JoeNBC as exec producer of a tv show with a female lead — how offensive to tell @HillaryClinton to smile. Only cause she's a woman!" tweeted David Holden.

Several women commented that his remark was condescending, while others replied with photos and GIFs of creepy smiles or that of Broad City's Abbi Jacobson and Ilana Glazer using their middle fingers to smile.

However, responses to the tweet really gained traction when Full Frontal host Samantha Bee — of Daily Show fame — replied with a photo tweet of herself frowning along with the caption: "Ladies, it's very important that you #SmileForJoe." Women across the web replied in kind, with photos of their pets frowning or their young daughters or even of the Joker.

Scarborough first attempted to justify his tweet. "We've called @BernieSanders grumpy for a year. @HillaryClinton is tough as hell. She doesn't need this fake outrage," he tweeted on 16 March. He continued with a series of tweets, in which he noted that he did not see Clinton "as a woman anymore than I did Thatcher. I look at her as a tough candidate who can handle it."

He continued: "I've also made no secret of the fact I like HRC personally and respect her toughness. She's dealt with a helluva lot more than a tweet." Scarborough appeared to somewhat understand where the outrage was coming from later on, but his critics remain steadfast.

As The Washington Post noted, several studies have shown that female leaders face a "double bind" issue, in that they are expected to hold the stereotypical leadership ideals — tough, assertive, bold and serious—but they are also expected to conform to gender norms held for women.

"We believe not only that women are nurturing, but that they should be nurturing above all else," explained Deborah Gruenfeld, a professor of leadership and organisational behaviour at Stanford University. "When a woman does anything that signals she might not be nice first and foremost, it creates a negative impression and makes us uncomfortable."

It should be noted that Clinton did in fact smile during her victory speech. She not only smiled but did so more than fellow victor across the aisle Donald Trump.