Biden back on road after clinching rancorous Trump rematch

President Joe Biden plunges back into his grueling election campaign schedule Wednesday, a day after he and rival Donald Trump set up one of the longest and most bitter White House races in US history.

Biden heads for a two-day swing through the battleground states of Michigan and Wisconsin -- both of which he flipped from Republican Trump in their 2020 showdown and needs to win again to secure a second term.

Incumbent Biden, 81, and former president Trump, 77 confirmed on Tuesday what already seemed a foregone conclusion when they each won enough delegates to clinch their parties' nominations for November's election.

The United States now faces a pivotal but rancorous battle stretching out over nearly eight months, with the country's oldest ever pair of election candidates making no secret of the personal bitterness between them.

While on the road Biden will seek to focus on his favorite, positive themes about boosting the economy, announcing a series of infrastructure investments while in Milwaukee, Wisconsin on Wednesday.

He will also speak at campaign events in both Milwaukee and then in Saginaw, Michigan on Thursday, during which he will likely continue his assault on Trump.

Michigan and Wisconsin are part of the "Blue Wall" -- along with Biden's birth-state of Pennsylvania -- that Trump won in 2016 after they spent years in Democrat hands, and which Biden then narrowly wrenched back four years later.

Biden embarked late last week on a tour of swing states, buoyed by a fiery and well-received State of the Union speech in which he again took aim at Trump.

 'Revenge and retribution' 

In a sign of the months of acrimony that lie ahead, both men lashed out at each other after their nomination wins on Tuesday, with Biden assailing Trump's "campaign of resentment, revenge, and retribution."

He singled out his rival's first-day promise to pardon the Trump supporters who assaulted the Capitol on January 6, 2021 to overturn Trump's election loss, saying they "placed a dagger at the throat of American democracy."

Real estate magnate and former reality TV star Trump faces a string of criminal cases including over the Capitol attacks, while Biden has also compared him to the Nazis for his harsh rhetoric on migrants.

Trump hit back by calling Biden on social media the "Worst, Most Incompetent, Corrupt and Destructive President in the History of the United States."

The pair's caustic rivalry has spilled over into many aspects of America's increasingly toxic political life.

On Tuesday, testimony by the US special counsel who investigated Biden's handling of classified documents and made controversial remarks about his age and memory quickly turned into a partisan slugfest.

Democrats and Republicans seized on the contrasting behavior of Biden and Trump -- who has been indicted for his own mishandling of top-secret documents and also faces questions over age-related flubs.

US standing on the international stage is also being affected, with allies alarmed as Republicans in Congress block $60 billion in vital military aid for Ukraine to fight Russia's invasion.

Biden authorized $300 million in emergency aid for Kyiv on Tuesday. Trump, in contrast, has threatened to cut aid and encouraged Russia to invade NATO countries that don't meet their financial pledges.