In an article published on Friday, liberal website Vox outlined serious concerns about Democratic presidential front-runner Joe Biden's mental fitness.

Citing his performance on the debate stage Thursday evening in Houston, Vox senior correspondent Zack Beauchamp levied that former Vice President Biden, 76, did not seem to have a firm hold of his faculties and was more than just "gaffe-prone." The article asserted that several answers the current front-running candidate gave throughout the evening "made the question of Biden’s mental fitness for office impossible to ignore."

"It’s an awkward topic that can easily verge into outright ageism," the article said of discussing Biden's mental capacity. "But Biden sounds sloppier and less put together than the other two frontrunners from his age bracket, Sens. Bernie Sanders (78) and Elizabeth Warren (70). He’s always been gaffe-prone, to be sure, but something about it feels worse now to a lot of Democratic voters."

Beauchamp noted that while specific incidents of Biden's debate performance gathered significant controversy and media attention, there was a moment that gave them significant pause that did not ruffle as many feathers.

In addition to a now notorious exchange in which former Secretary of Housing and Urban Development Julián Castro repeatedly asked Biden if he was "forgetting what [he] said two minutes ago," Biden received attention for suggesting parents "have the record player on at night" to give their children an academic advantage.

"But another Biden moment also raised red flags," Beauchamp said: "His response to a question about the Obama administration’s withdrawal from Iraq."

"Foreign policy is supposed to be one of Biden’s clear areas of competence, a policy area he’s focused on throughout his career," Beauchamp noted. "But that’s not what happened. After asserting that the withdrawal wasn’t a mistake, Biden instead talked for a bit about his support for the initial invasion of Iraq back in the Bush administration."

Outlining the perceived inaccuracies in Biden's recollection of his role in the withdrawal of U.S. troops from Iraq and support of the initial invasion, the article points out that Biden's response to the question seems to lack clarity.

"Things get weirder when Biden gets to the actual meat of the question, about whether the Obama Iraq withdrawal was a mistake," Beauchamp writes. "He offered two short paragraphs — one recounting his role running Iraq policy under Obama, and a second that frankly makes no sense."

Biden's answer in question, which included references to President Barack Obama and a personal anecdote about his son, did not directly address the moderator's query.

"It was later, when we came into office," Biden said during the Thursday debate, "that Barack turned — the president turned to me and said, ‘Joe’ — when they said we’ve got a plan to get out, he turned to the whole security and said, ‘Joe will organize this. Get the troops home.’"

"My son spent a year in Iraq, and I understand. It made — and we were right to get the combat troops out," he continued. "The big mistake that was made, which we predicted, was that you would not have a circumstance where the Shia and the Kurds would work together to keep ISIS from coming — from moving in."

Reiterating Biden's comments about the Shiites and Kurds, Beauchamp suggests this was the most confusing moment of the exchange. "I’ve spent a while pondering this last line," he writes. "And I can’t make heads or tails of it."

"The overall impression was of Biden just saying some Iraq-related things that either didn’t address the question or were literally incoherent," the article states in scathing criticism. "And this is a policy area he specialized in, both during his time in the Senate during the Bush administration and as Obama’s vice president."

Detailing two other foreign policy question flubs, Beauchamp suggests that Biden's answers are "worrying."

"Why is Biden seemingly porting over dubious concepts from Iraq to another conflict entirely?" he asks. "Why were major portions of his answers on both Iraq and Afghanistan so deeply flawed? Why did he perform so poorly in this area of alleged competence? These are worrying questions."