Former New York Congressman Anthony Weiner took a jab at Democratic presidential nominee Bernie Sanders Saturday in an op-ed for Business Insider.

Weiner, who admits that Sanders is his "kind of politician," asks Sanders just what he thinks he's doing in the 2016 race.

'Still, I have one major question for Bernie. What exactly does he think he's doing in a Democratic presidential primary? Why is he asking for the nomination of a party he always avoided joining?" Weiner asks, referring to the fact that Sanders is an Independent running for the Democratic ticket.

Weiner admits that he completely understands "Bernie Mania" in Sanders' quest to unseat Democratic frontrunner Hillary Clinton for the 2016 presidential ticket, but wants to know why "[a]fter a career of steadfastly insisting that the Democratic party was not his home" does he want to "not only be a member" of the Democrat party but be its "standard bearer."

"What changed?" Weiner asks.

Sanders is "right about a lot of things" such as healthcare and income inequality, Weiner admits, but if he "wants to lead this party, he needs to explain what he's doing here in the first place."

Weiner served as New York's 9th Congressional District from 1998 until his resignation for a sexting scandal in the summer of 2011. His wife, Huma Abedin, has been a long-time aide to Hillary Clinton and currently serves as vice chairwoman of Clinton's 2016 presidential campaign.

Sanders is the longest-serving Independent in U.S. congressional history, having been elected to represent Vermont in 2006. A self-described socialist, he announced his intentions to seek the nomination for the 2016 Democratic Party in April.

Though once considered a long-shot, Sanders has caught up to former Secretary of State Hillary Clinton in New Hampshire.