WASHINGTON (AFP) - Mr Joe Biden, striving to win over still-undecided voters who could swing the US presidential election against Mr Donald Trump, is sparing no effort to broadcast one of his most potent weapons: endorsements from many of his former Republican opponents.

From handing Republican stalwarts prime-time speeches at the Democratic National Convention to welcoming endorsements from hundreds of former staff members to Mr George W. Bush, Mr John McCain and Mr Mitt Romney, the presidential challenger is waving his bipartisan credentials high.

But will it work?

Ms Kari Walker, a 50-year-old Wisconsin resident who has backed Republican candidates for two decades, plans to vote for Democrat Biden on Nov 3.

Ms Walker, who two weeks ago told AFP she could not bring herself to vote for Mr Trump - "a worse president than I could have imagined" - felt reaffirmed by the stance of the former Republican staff members.

"I found the support of GOP stalwarts to be persuasive," said Ms Walker, who with her husband owns a tavern in the small town of Reedsburg, in a county that backed Mr Trump in 2016 after twice voting for Democrat Barack Obama.

"I would be voting for Biden regardless, but I appreciate GOP influencers crossing over," she said in an e-mail on Friday (Aug 28), referring to the Grand Old Party, a traditional nickname for Republicans.

Ms Walker is exactly the type of voter that the former vice-president's campaign hopes to lure by welcoming those from across the aisle.

While Mr Obama's former No. 2 continues to lead Mr Trump in polling nationwide, the president has narrowed the gap in certain key states, those that regularly "swing" back and forth between Republicans and Democrats - and which can therefore decide a close election.

The billionaire Republican has been courting them openly, warning against the "anarchy" he says a Biden presidency would bring, which he says could lead to the "destruction" of the nation's leafy - and mostly white - suburbs.

The Republican convention heard from some former Democrats, their presence designed to underscore Mr Trump's outreach to those crucial battleground states.

'WE'VE LOST OUR MORAL COMPASS'

But Mr Trump appears to be benefiting from less party-switching than Mr Biden, who has worked to persuade voters disappointed, even disgusted, by TMr rump's style and stewardship, notably of the coronavirus pandemic that has claimed more than 180,000 American lives.

"This is not an easy decision for Republicans to make," wrote the former staff members of Mr McCain, the late Republican senator and 2008 presidential candidate who had a mutually disdainful relationship with Mr Trump.

"Given the incumbent president's lack of competent leadership, his efforts to aggravate rather than bridge divisions among Americans, and his failure to uphold American values, we believe the election of former vice-president Biden is clearly in the national interest," they wrote in an open letter.

The former Bush staff members sounded a similar tone.

"The onslaught of insults and vulgarity we have witnessed in recent years must stop," they said.

"We have lost our moral compass."

Mr Glenn Kessler, a Washington Post journalist, expressed surprise over that message.

"I personally know a number of these people and how deeply conservative they are on many issues," he wrote on Twitter.

"I never imagined they would publicly endorse a Democrat for prez."

Beginning in the spring, several groups of anti-Trump Republicans, including the Lincoln Project, have announced their support for Mr Biden.

'LAPSED REPUBLICANS'

But since the Democratic convention opened on Aug 17, the persuasion campaign has taken on new intensity.

Mr John Kasich, a former Republican governor of the swing state of Ohio, was given a prime speaking spot on that first night.

On the following night, Mr Colin Powell, who was secretary of state to Republican President Bush and a controversial advocate of the war with Iraq, had the Democratic limelight.

Both men got much more speaking time than one of the most high-profile progressive members of Congress, the young New Yorker Alexandria Ocasio-Cortez, a decision that many in the party's left wing found offensive.

And last Monday, the opening day of the Republican convention, the Biden team announced the support of some 20 former Republican members of Congress.

"These lapsed Republicans are emblematic of the many former Republican voters concentrated in affluent, growing, and highly educated suburban areas who have been leaving the GOP in the Trump era," said Mr Kyle Kondik, a University of Virginia political analyst.

But he added a caution: "That said, I don't know if these endorsements actually move new voters out of Trump's camp."