Vice President Kamala Harris' replacement of President Joe Biden on the Democratic ticket could keep the electoral battlefield confined to the typical handful of swing states after the electoral map appeared to be mushrooming in Republicans' favor.

After Biden's ruinous debate performance last month, Republicans boasted and Democrats feared that blue and blue-leaning states like New Hampshire, New Mexico, Virginia and even New Jersey were suddenly in play. But now, operatives in both parties predicted that having a Democratic nominee who's not dogged by such weighty baggage takes those states back off the table, recalibrating the race back to the Rust and Sun Belts.

"She definitely helps us play less defense," one source familiar with Harris' campaign's strategy said. "States that were blue-leaning states that became more competitive post-debate based on early polling seem to be shifting back."

Democratic alarm was high after last month's debate, when Biden's bumbling performance sent Democrats into a tizzy and had Republicans dreaming about a landslide victory.

Handwringing over traditional swing states like Michigan, Pennsylvania and Wisconsin in the Rust Belt and Arizona, Georgia, Nevada and North Carolina in the Sun Belt was exacerbated by discussions of having to bolster states where Democrats should waltz to victory but could prove competitive as Biden's poll numbers cratered.

"I was getting calls pretty much on a daily basis with concern," said Henry Roybal, the chair of the Santa Fe County Democratic Party in New Mexico.

Now, "New Mexico is off the map," he said.

The story is the same elsewhere.

Conversations with operatives in traditionally noncompetitive states echoed Roybal's account, even if they believe that former President Donald Trump still would have struggled to carry their electoral votes and there wasn't definitive polling to prove he could.

After the debate, one senior New Jersey Democratic strategist insisted Biden could have won their state by a mid-single-digit margin after winning it by about 16 points in 2020. The state is now "completely off the table," the person said.

Some Republicans aren't entirely convinced.

Harris ran a dysfunctional 2020 presidential campaign and had to drop out before any primary votes were cast, and her approval ratings at the start of her nascent campaign are low. And while the blue-leaning states are still safer for Harris than traditional swing states, Republicans maintain any slip ups could keep them in play.

"It all depends upon how Kamala Harris runs her campaign and how she performs under the enormous pressure of a presidential contest. She did not acquit herself well when she ran for the 2020 nomination," said GOP pollster Whit Ayres." If she's a whole lot better than she was then, then conceivably, those states could be off the table again. On the other hand, if she does not perform well, I think all those states are potential Trump pickups."

Trump is not giving up on those states. He is blitzing Harris with attacks on her record, labeling her a "California liberal," and will hold his second joint rally with Ohio Sen. JD Vance, his running mate, in St. Cloud, Minn, on Saturday, firing up his voters in a state no Republican presidential candidate has won since 1972.

"As more voters understand how dangerously liberal Kamala Harris is, President Trump's chances in these traditionally-Democrat strongholds will only get better," said Trump campaign spokesperson Karoline Leavitt.

Still, other Republicans concede that Harris' candidacy introduces stiffer headwinds than existed when Biden topped Democrats' ticket. Underscoring the point, a New York Times/Siena College poll released Thursday found Harris and Trump statistically tied, an improvement from earlier this month when the same poll found Trump ahead of Biden by 6 points.

"I expect Harris will be stronger. I mean, you just can't help but be stronger, regardless of performance level," said New Hampshire GOP strategist Mike Dennehy. "And so now it's just a question of how well she does on the stump and in debates."

"It's too early to know exactly, but my overall summary is she probably stems the bleeding and raises the floor, but it doesn't necessarily mean that she's going to be able to put away states that she needs to," Virginia-based Republican strategist Zack Roday added.

Now, the race is expected to shift back to the seven swing states that were at the top of the battleground map at the start of the race, with the source familiar with the campaign's strategy telling ABC News "we're seeing a reversion to what we expected this race to be pre-presidential debate."

All seven states are anticipated to be decided by razor-thin margins, with millions of dollars dumped in by both campaigns. Already, Harris has hit the campaign trail in Wisconsin, a marquee swing state.

Harris' campaign released a memo Wednesday saying it "intend[s] to play offense in each of these states, and have the resources and campaign infrastructure to do so."

"This campaign will be close, it will be hard fought, but Vice President Harris is in a position of strength – and she’s going to win," Campaign manager Jennifer O’Malley Dillon wrote.

Taking Republicans' stretch states off the table as much as she can is a key part of remaining competitive in the true battlegrounds. The universe of campaign finance is gargantuan but finite -- and every dollar spent in New Jersey or New Mexico is one not spent in Arizona or Michigan.

"The one thing it likely changes is, right now, the ground game," said one national GOP strategist. "Are they going to shift resources out of specific swing states into other states because the map doesn't feel as large for Democrats anymore to have to defend territory?"

And Harris' ability to prevent a landslide for Trump is not just key for her -- it's also important for Democrats' hopes for the House of Representatives and Senate.

Several key down-ballot races are being held in both swing states and blue-leaning states, and Harris' ability to keep the margin at the top of the ticket competitive in battlegrounds and expansive in states she wins -- rather than a blowout for Trump, as was speculated with Biden -- would be a massive boon to congressional contenders.

"It's critical. If you're a Senate or a governor candidate or a congressional candidate, you can run ahead of the top of the ticket by a handful of points, three or four. You can't run ahead at the top of the ticket by 10 or 12 points," Ayres said.

Biden, he added, "definitely could have gotten blown out."