WASHINGTON, July 24 (Reuters) - President Joe Biden on

Wednesday said dropping out of the race for the presidency and

endorsing his vice president, Kamala Harris, as the Democratic

candidate was the best way to unite the country, despite his

ambition to win a second term.

Biden's announcement to not seek re-election on Sunday

followed a disastrous June debate with Trump that exacerbated

questions about his ability to win, or to serve another four

years if he succeeded.

In his address to the nation from the Oval Office, he said

he believed he earned reelection because of his record during

his first term.

"But nothing, nothing can come in the way of saving our

democracy. That includes personal ambition," he said. "So I

decided the best way forward is to pass the torch to a new

generation. That is the best way to unite our nation."

Harris, the first Black woman and Asian American to serve

as vice president, would become the first woman elected

president if she prevails on Nov. 5. In the three days since

Biden's decision, Harris has pulled in broad support across the

Democratic Party and revitalized its election campaign.

Biden praised Harris as a strong leader who would make an

effective president.

"She's experienced, she's tough, she's capable. She's been

an incredible partner to me and a leader for our country. Now

the choice is up to you the American people."

Hours earlier, Republican presidential candidate Donald

Trump tried to quash some of that momentum in an aggressive

speech at the rally, his first since Harris' emergence changed

the race. "She is a radical Left lunatic who will destroy our

country if she ever gets elected," he said.

Trump routinely uses insults in attacking his opponents and

made clear he planned to ignore advice that he take a softer

line. "I'm not gonna be nice!" he told his cheering supporters

in Charlotte.

He attacked Harris as a driving force in the Biden

administration who should be held responsible for its policies

on immigration and other issues.

"As border czar, Kamala threw open our borders that allowed

20 million illegal aliens to stampede into our country from all

over the world," Trump said.

"I will terminate every single open border policy of the

Biden Harris administration and we will seal the border and we

will stop Kamala Harris invasion without delay," the former

president said.

Biden put Harris in charge of working with countries in

Central America to help stem the tide of migration, but she was

not given responsibility for border security nor was she named

"border czar."

Trump also touched on abortion, an issue that Democrats had

long seen abortion rights as a winning issue for them.

"When you compare my position on abortion to that of Kamala

Harris, my position is eight points higher in the polls. And

that's because she is so radical," he said.

Harris has served as point person for the Biden

administration on the issue of abortion, which is expected to

become even more central to the campaign with her at the top of

the ticket.

'PASS THE TORCH'

Biden said he intends to focus on his work as president in

the six months left in his term.

"That means I will continue to lower costs for hard-working

families and grow our economy. I will keep defending our

personal freedoms and our civil rights - from the right to vote

- to the right to choose," he said, according to his prepared

remarks, outlining some themes that Harris is expected to build

her campaign around.

The president returned to Washington on Tuesday afternoon

after isolating with COVID at his home in Delaware, where he

made the announcement that he was ending his campaign.

The Democratic National Committee's rules committee agreed

on Wednesday on a plan to formally nominate Harris as soon as

Aug. 1 - before the party's Aug. 19-22 convention in Chicago -

with Harris picking a running mate by Aug. 7.

Earlier on Wednesday, the 59-year-old vice president called

on a rally of more than 6,000 Black women in Indianapolis to

help her revitalize the Democratic campaign.

Harris spoke at an event in Indianapolis hosted by the Zeta

Phi Beta Sorority, which was founded at Howard University, the

historically Black college she attended. She hopes to tap

sororities' multi-generational network of Black women - who

played an important role in Biden's 2020 victory - to deliver

strong voter turnout for Democrats again in November.

"I thank you. And now, in this moment, our nation needs your

leadership once again," Harris said.

Trump, coming off a triumphant week in which his party

unified around his presidential bid after a failed assassination

attempt two weekends ago, has had to watch as Biden's sudden

departure from the race shifted the narrative and sparked a

surge of attention toward Harris at his expense.

Harris and Trump are closely competitive, public opinion

polls showed this week.

A Reuters/Ipsos poll completed on Tuesday showed Harris with

a marginal two-percentage-point lead over Trump, 44% to 42%. A

CNN poll conducted by SSRS showed Trump leading Harris, 49% to

46%. Both findings were within the polls' margins of error.

The Harris campaign on Wednesday said it has raised $126

million since Sunday, with 64% of donors making their first

contribution of the 2024 campaign.