Minnesota Rep. Dean Phillips may not have a strong chance of winning the Democratic nomination, but his primary challenge poses a real danger to President Joe Biden's reelection campaign. Phillips officially announced his candidacy this week, focusing on the first-in-the-nation primary state of New Hampshire, where Biden won't even be on the ballot in January. While Democratic voters have shown little interest in backing anyone other than Biden, Phillips is targeting the president's age as a potential weakness. Phillips, who is 54 years old, argues that Biden's five decades in federal office are "part of the problem." This argument could garner support from primary voters who have concerns about Biden's age. However, the real danger for Biden lies in the exposure of his vulnerability. Polls show that concerns about Biden's age and ability to lead for another four years are already his greatest weakness with swing voters. Phillips' primary attacks could amplify those doubts and provide ammunition for Republicans in the general election. Biden's absence from the New Hampshire primary ballot has also led to write-in efforts by Democrats in the state, who are organizing to ensure votes for the Democratic incumbent. The president's decision not to comply with Democratic National Committee calendar guidelines has further diminished the state's standing in the early nominating process. Although Biden may still have a path forward in the New Hampshire primary, his vulnerability and lack of presence on the ballot could be a cause for concern in his bid for reelection.