President Joe Biden and former President Donald Trump are still facing resistance from significant portions of their respective voter bases.
In recent primaries in New York, Wisconsin, Connecticut, and Rhode Island, both parties witnessed holdouts who did not support the main candidates.
While there were more Republican holdouts, indicating a lack of support for Trump, Biden faced a more acute problem because the dissent against him was strongest among the core Democratic base.
Although Tuesday's primaries were not competitive, they highlighted Biden's need to strengthen his base.
In states like Connecticut and Rhode Island, where "uncommitted" was an option, and Wisconsin, which had an "uninstructed delegation" ballot line, Biden showed signs of weakness, with the protest vote against him breaking 10 percent in some areas.
Democratic voters in cities with a significant college presence, such as New Haven, Providence, and Madison, showed a considerable anti-Biden sentiment, which could be concerning for Biden as these areas have been crucial for Democrats in recent elections.
Trump also faced challenges within his party, particularly in suburban areas.
Even though Nikki Haley dropped out of the Republican presidential primary weeks ago, she still received significant support in upscale areas like Westport and Greenwich in Connecticut, as well as in the WOW counties around Milwaukee, Wisconsin.
In New York, Haley received over 20 percent of the vote in counties like Monroe, Tompkins, and Manhattan.
However, it's unclear if there was a significant protest vote against Biden in New York, as blank ballots submitted by upset Democratic voters won't be counted until the results are certified.
While primaries do not determine general election outcomes, they indicate areas where candidates need to improve their support.
Biden, in particular, needs to make up more ground as Trump currently leads in the polls in six of the seven swing states. Both candidates have work to do to solidify their bases before the November election.