Donald Trump has a new strategy: Attack Kamala Harris (and Joe Biden)

WASHINGTON − It's on to Plan B for the Donald Trump campaign .

After years of running against President Joe Biden , the Trump campaign is re-tooling to face another Democratic opponent, most likely Vice President Kamala Harris .

Trump aides declined Sunday to detail strategy in the hours after Biden's withdrawal announcement , but in recent days they have confirmed the general idea: Attack both Harris and Biden.

In addition to ads linking Harris to border security - she was put in charge of the migration issue during the Biden presidency - the Trump campaign also signaled they will argue that Biden should resign and the Democrats as a party should be held accountable for all that has happened.

"He is not fit to serve," Trump told Fox News Digital just minutes after Biden's announcement. "And I ask - who is going to be running the country for the next five months?"

More: Joe Biden drops out of 2024 race and endorses Kamala Harris

The Harris campaign against Trump

Democrats pointed out that Harris, a former prosecutor, can more easily exploit Trump's legal troubles, from his conviction in the New York hush money case to a civil judgement finding him liable for sexual abuse .

Others noted that Harris is the first Black woman to serve as vice president, and predicted that Trump's revamped campaign will also rely on race and gender.

"Expect racist and misogynist undertones coming from the Trump campaign for the remainder of the campaign," said Rodell Mollineau, former spokesman and senior aide for the late Senate Majority Leader Harry Reid, D-Nevada.

Trump's new strategy will also include defense.

Opponents signaled that they will use another issue against Trump: Age. With Biden out of the race, the 78-year-old Trump is the oldest major party nominee in U.S. history.

More: Donors hail Biden: Harris 'jolt of adrenaline' will energize Democratic base

"The focus moves from President Biden to squarely on Donald Trump's old age, physical infirmities, and obvious mental decline," said a memo from the Lincoln Project, an anti-Trump organization.

During last week's convention, Trump and his allies said they were developing a campaign plan against Harris, including attack ads regarding her years as vice president and California attorney general. (One potential Democratic counter: Trump actually contributed $5,000 in 2011 to Harris' reelection campaign.)

The Trump campaign has already begun internal polling on a Trump-Harris matchup. Officials would not release data; in his brief CNN interview, Trump claimed Harris would be easier to beat than Biden.

At the Republican convention in Milwaukee, speaker after speaker criticized both Harris as well as Biden over illegal border crossings and high rates of inflation.

Tying H arris to Biden

Expect Trump and his surrogates to continue linking Harris to Biden, including the way in which she would replace him at the top of the Democratic ticket.

"If Democrats rally around Harris, Trump can be expected to say this was an inside job by the party bosses to subvert democracy," said pollster Frank Luntz.

Sen. Steve Daines, R-Mt., chairman of the Senate Republican campaign committee, noted that no Democratic leaders have called on Biden to resign the presidency and for Harris to replace him in the Oval Office.

"This leads me to believe they think she is unqualified to serve as Commander-in-Chief," Daines said.

In a post on X, Trump running mate JD Vance said Harris has been with Biden "every step of the way," and "owns all of these failures." Vance said he and Trump are ready for "whoever's at the top of the Democrat ticket. Bring it on."

Democrats said Trump and Vance will need a new strategy.

Joe Trippi, longtime Democratic aide who ran Howard Dean’s 2004 presidential campaign, said Biden is passing the torch not just to Harris, but to "an entire new generation of leaders in the Democratic Party."

Said Trippi: "The eyes of the nation now are on the future and that is a fight Trump, JD Vance, MAGA and Project 2025 will not win."

This article originally appeared on USA TODAY: Donald Trump has a new strategy: Attack Kamala Harris (and Joe Biden)