Vice President Biden will make his first campaign stop for Hillary Clinton Hillary Diane Rodham ClintonBiden leads Trump by 36 points nationally among Latinos: poll Democratic super PAC to hit Trump in battleground states over coronavirus deaths Battle lines drawn on precedent in Supreme Court fight MORE on Wednesday night at the Democratic National Convention, an important show of unity for two political heavyweights who haven’t always seen eye to eye.

Biden openly considered running for president against Clinton for months before concluding last fall that it was too late for him to enter the race.

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When Biden backed Clinton for president in June, he made his endorsement in a perfunctory fashion.

And he has sometimes made critical comments about the former secretary of State, firing up speculation that Biden thinks he should be the Democrat seeking to extend President Obama’s legacy.

In Philadelphia, however, any sentiment Biden has about running for president will be put aside.

While the convention is likely to celebrate Biden’s long career, allies say he is determined to use his address to help Clinton defeat Donald Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE, the GOP presidential nominee.

Biden will outline why “Clinton is the only candidate with a record of standing up for the middle class, and why she’s best equipped to build on the administration’s economic policies that have moved our economy from crisis to recovery to the cusp of resurgence,” according to a vice presidential aide.

Confidants say Biden, a longtime member and chairman of the Senate Foreign Relations Committee, will zero in on the argument that Clinton is ready to lead the nation and that Trump is not.

“He cares very much about the country and he wants the country to have knowledgeable, competent leadership,” said former Sen. Ted Kaufman (D-Del.), who for years served as Biden’s chief of staff and succeeded him as senator after Biden became vice president.

“It’s a dangerous world out there. People want leaders who are experienced, [especially] in foreign policy,” Kaufman said.

Biden’s concerns about Trump were amplified by the recent terrorist attack in Nice, France, and the coup attempt in Turkey, an important NATO ally. Trump pinned blame for both events on the foreign policy of Obama and Clinton, arguing their efforts to fight terrorism have fallen short and bred instability in the Middle East.

Biden and Clinton have been at odds in major foreign policy debates, including troop levels in Iraq and Afghanistan and the raid that killed al Qaeda leader Osama bin Laden.

But Democratic strategist Brad Bannon dismissed those squabbles as “inside baseball,” arguing Biden could counter Trump while vouching for Clinton’s character and experience.

“He worked with her closely as secretary of State and in the Senate,” Bannon said of the vice president. “He knows how to do this stuff. I am sure he can do a fine job addressing Hillary’s bona fides without dwelling on the differences.”

Biden has long been seen as a powerful potential surrogate for Clinton, who is polling worse among white men, particularly those without college degrees, than Obama did in his elections.

The vice president hails from blue-collar Scranton, Pa., and is seen as someone who can vouch for Clinton with union workers and so-called Reagan Democrats.

It’s help Clinton needs across the country, and particularly in Pennsylvania and Ohio, two big swing states.

“Every Democrat likes him,” said Bannon. “He is a great asset who has a folksy appeal. … My guess is Biden is going to spend a lot of time in Ohio and Pennsylvania.”

Following the convention, Biden is expected to serve as a surrogate for Clinton in Rust Belt states targeted by Trump.

The vice president was expected to make his first joint appearance with Clinton earlier this month in Scranton, but that event was scrapped after a sniper killed five police officers in Dallas.

Biden could also make an appeal to supporters of Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.), Clinton’s former rival for the nomination, to get on board.

The vice president frequently lauded Sanders during the primary. In January, he praised Sanders’s focus on income inequality and called Clinton “relatively new” to the issue.

Those comments could give Biden added credibility with Sanders backers, many of whom have been reluctant to support his former foe.

Biden has been eager to play the role of attack dog against Trump, using his everyman appeal to undercut the GOP standard-bearer.

The vice president took a shot at Trump during a June speech in Ireland, blasting “reactionary politicians and demagogues” who blame economic and social problems on immigrants by “peddling xenophobia, nationalism and isolationism.”

Still, a part of Biden is likely to be thinking about what might have been when he takes the stage in Philadelphia to fete Clinton.

After his son, Beau, died from brain cancer in May 2015, the vice president wrestled throughout the summer and into the fall with whether to launch his own presidential campaign.

He ultimately concluded that he was not ready for such a massive undertaking so soon after the death of his son. But he has sometimes expressed wistfulness about that choice.

He said he “would have been the best president” during a May interview with ABC News.

Biden loyalists have long felt that Clinton’s allies boxed him out of the 2016 race, denying a chance for a two-term vice president to claim the mantle of Democratic heir apparent.

That frustration reached a boiling point when, days before Biden revealed his intention not to run, top Clinton adviser John Podesta said it was “time he make that decision.”

Clinton supporters, in turn, were angered when Biden attempted to take credit for the bin Laden raid, when it was the former secretary of State who argued forcefully to launch the operation at the terrorist’s Pakistani compound.

But Democrats ultimately believe Biden will go above and beyond to help elect Clinton, something that Obama views as essential to protecting his legacy.

“I am sure he is thinking all the time, ‘What if,’ ” said Bannon.

“The reality is, if things had been different … there’s an even chance Joe Biden Joe BidenBiden leads Trump by 36 points nationally among Latinos: poll GOP set to release controversial Biden report Can Donald Trump maintain new momentum until this November? MORE could be speaking on Thursday accepting the nomination,” he said. “But the reality is Biden is a pro. He’ll go out there and do what he needs to do for Hillary.”

Kaufman, who is as close to Biden as anyone in his inner circle, had an even more definitive answer when asked whether the vice president will have thoughts of remorse at the convention.

“No, I don’t think so,” he said.