WASHINGTON — As quickly as his pivotal political comeback in South Carolina resurrected Joe Biden’s presidential campaign and catapulted him to success on Super Tuesday, it also renewed an urgency for the Trump campaign to reload its attacks against the former vice president.

For the better part of 2019, President Donald Trump’s allies treated Biden as the presumptive front-runner and spent considerable time and resources criticizing him. The president's own focus on Biden as a potential general election opponent was the focus of his impeachment in the House of Representatives (and later acquittal in the Senate) for attempting to pressure the Ukrainian president to launch, or at least announce, an investigation into unproven allegations against Biden and his son, Hunter.

In recent weeks, as Biden's fortunes in the Democratic primary were dimming, the Trump team's focus shifted towards to Vermont Sen. Bernie Sanders as he racked up victories or near-wins in Iowa, New Hampshire and Nevada. "Socialism" and "crazy Bernie" references outnumbered "sleepy Joe" at his rallies and in GOP talking points.

Now, as the sometimes pundit-in-chief acknowledges, Biden has bounced back and the Trump re-election team is working to slow his momentum in the hopes of a drawn-out Democratic nomination fight. “He is just as terrible a candidate right now as he was a few days ago,” Trump campaign manager Brad Parscale said of Biden in a statement after Super Tuesday.

Trump himself, however, predicted Biden would eventually prevail during a Fox News town hall on Thursday, coincidentally held in Biden’s hometown of Scranton, Pennsylvania. The president said he was “all set” to take on Sanders before Biden’s impressive campaign revival, wagering that “Bernie would be tougher” as the nominee because of his fervent following.

Despite the public bravado, senior campaign officials have long been concerned privately about a head-to-head matchup against Biden in the general election, specifically in key Rust Belt states.

One of the main arguments the president has already deployed against Biden is to question his mental acuity and physical stamina, a similar playbook to the attack on Hillary Clinton’s health in 2016.

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The president has repeatedly questioned Biden’s sharpness, telling raucous crowds he predicts the former vice president, if elected, would be “in a home” while his aides ran the country. The same kind of attack usually includes mockery of “gaffe-prone” Biden, which has been a theme following Biden’s occasional tendency to misspeak.

“I don’t want to be too critical, but I’ve never seen anything like it, to be honest,” Trump told Sean Hannity in an interview on Fox News Wednesday night.

It’s an argument echoed by his top surrogates, including his daughter-in-law Lara Trump. “Who would be running the country if this individual really is not showing he is functioning with all gears moving here? And I mean, I think it's fair to call that out and ask what is going on,” she said on Fox News Wednesday.

The campaign also plans to use Democrats’ own words against Biden, questioning his acumen and astuteness. A slickly edited video released by the rapid response arm was re-circulated this week, which includes Sen. Cory Booker, D-N.J., then a candidate, saying last year: “There’s a lot of people who are concerned about Joe Biden’s ability to carry the ball all the way across the end line without fumbling.”

For months, the campaign has claimed it has no preference for the Democratic candidate they will meet in the general election but aides have privately expressed a desire for facing Sanders, whom they believe would provide an easier and more extreme contrast as a self-proclaimed “democratic socialist.”

Much like the rest of the Democratic field, senior Trump campaign officials did not see Biden’s swift resurgence coming. They had all but stopped their attacks on Biden and Ukraine once the impeachment trial came to an end.

Now, as the three-time presidential hopeful's prospects rise again, the campaign is resuscitating discredited claims about Hunter Biden, with Trump committing to use them “all the time” and make it a “major issue” in the coming months.

Republicans have also signaled they will ramp up an ongoing investigation into the Bidens and Burisma, the energy company whose board Hunter Biden served on while his father was vice president. Sen. Ron Johnson, R-Wis., said this week he’d like to move quickly and possibly release an interim report in the coming weeks.

Democrats dismiss the inquiry as purely political, arguing that GOP lawmakers are only reviving the investigation now that Biden has exceeded expectations in recent primary contests.

“Donald has a history of awful strategic judgment when it comes to Joe Biden. For example, he is the only American president who has ever tried to force a foreign country to lie about the candidate he's too afraid to look in the eye," Biden campaign spokesman Andrew Bates said in a statement to NBC News.

"Betting on these worn-out, feckless attacks would accomplish just one thing: giving us the perfect opportunity to tee up his worst liabilities. Panic often drives people to make poor decisions."

The Trump team's preference would be to see a contested Democratic convention, believing that the divisions would only benefit Trump. Even as that prospect becomes less likely with a shrinking Democratic field, the Trump campaign is seeking to capitalize on the divide between Sanders' more progressive supporters and the moderates backing Biden.

As part of that effort to prod at the divisions, Trump and his allies have publicly questioned whether the Democratic Party has “rigged” the primary to damage Sanders and elevate a candidate like Biden, who is seen as more compatible with them. With efforts like that, the Trump campaign believes they can appeal to the “populist passion” of Sanders’ base, much like they know how to do with the president’s most ardent fans.

The Democrat establishment came together and crushed Bernie Sanders, AGAIN! Even the fact that Elizabeth Warren stayed in the race was devastating to Bernie and allowed Sleepy Joe to unthinkably win Massachusetts. It was a perfect storm, with many good states remaining for Joe! — Donald J. Trump (@realDonaldTrump) March 4, 2020

The Trump team is also aiming at Biden on issues like trade deals supported by the longtime senator in the past, believing that trade policies supported by Biden and Obama will be beneficial to making a case that they were responsible for eliminating manufacturing jobs, especially in the Midwest.

When the Democratic nomination battle does wind down — whether in weeks or months — the focus will shift to the general election battle, putting the president and his campaign events into the daily conversation again and providing even more opportunities for the campaign to make its case against the nominee.

Through the primary season, Trump has shadowed Democrats as they held their primary contests, but for the first time in months, there are no major rallies on his campaign schedule in the coming weeks when Democrats vote in Idaho, North Dakota, Michigan, Missouri, Mississippi and Washington state.