Vice President Kamala Harris' momentum could be the result of Democrats feeling relieved they are running a candidate other than President Biden rather than her strength as a candidate, a GOP strategist says.

The Democratic ticket has seen a boost in several polls conducted since Biden withdrew his re-election bid, with surveys showing Harris performing better than the president against former President Trump.

A GOP strategist tells Fox News that the momentum might not be the result of Harris herself, but rather the Democratic Party feeling hopeful about a replacement for Biden.

"It’s mostly a reflection of the relief Democrats feel moving past the Biden campaign, which appeared doomed," GOP strategist David Kochel told Fox News Digital. 

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Fox News polling found that since Biden dropped out of the race, Harris has gained a slight lead over Trump in almost every swing state.

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Harris tied with Trump in Michigan, a state the former president was leading Biden by 8 points in January, according to a recent Detroit News WDIV-TV survey.

Additionally, Harris received a favorability boost of nearly 10 points over the course of one week after Biden withdrew from the race, according to an ABC News/Ipsos survey. 

Democrats have touted Harris' success rate and say that she is uniting the party.

"It is so remarkable how in a matter of days Harris has consolidated our big tent party, and this is something that is coming from the ground up," Transportation Secretary Pete Buttigieg told Fox News, describing a "level of energy that I haven't seen on the campaign trail in a long time."

However, Kochel told Fox that Harris' momentum will be tested after the Democratic National Convention in August, when she will likely be named the party's official 2024 nominee.

"If she sustains it through the convention, it will be more a reflection of her performance," Kochel said. "We’ll know in a month what to call it."