Former Vice President Joe Biden officially joined the Democratic presidential race on Thursday with an incendiary announcement video that focused on the deadly march in Charlottesville and portrayed Trump as a stain on American history who must be removed from power.

The 76-year-old former senator from Delaware plans to formally kick off his presidential campaign with an appearance at a Pittsburgh union hall on Monday. Biden has made his close ties with union workers a centerpiece of his until-now nascent presidential campaign in recent weeks, joining a picket line of striking grocery store workers in Massachusetts and telling a firefighters union in Washington that the United States “was built by the great American middle class—and unions built that middle class.”

Biden has led early polling of potential Democratic candidates for months, in part due to the name recognition that comes with serving two terms as President Barack Obama’s vice president, and his intention to run has become an open secret in recent weeks.

“My intention from the beginning was if I were to run would be the last person to announce,”  Biden told reporters after a speech in front of union workers in Washington, D.C., last month. “We’ll find out whether I can win in a primary.”

But in the widest and most diverse field of presidential contenders in the party’s history, Biden will have to combat concerns that his age, more moderate legislative and policy record, and recent questions about his interactions with women make him just another old white guy seeking the nomination.

“He operated at a different time and environment and will have a lot to answer for,” a former Obama-Biden aide told The Daily Beast last month. “Look at Hillary Clinton’s numbers before she got into the 2016 race. The most popular moment is when you're a prospective candidate and a statesman who can shape the field from the outside. Being in presidential campaigns tends to be diminishing for everyone except for the victor.”

With three decades in the U.S. Senate, followed by eight more years in the Obama administration, the former vice president has more experience in national office than any of the 20 candidates seeking the Democratic nomination, and would be the oldest person ever elected president if he were to win.

In those decades of experience, however, lurk potential landmines for any presidential candidate, particularly a presumptive frontrunner with nearly two dozen opponents seeking to bring him down. Biden’s first two presidential campaigns, in 1988 and 2008, ended disastrously after a plagiarism scandal and a racially insensitive gaffe about his future running mate, respectively, and Biden’s handling of Supreme Court Justice Clarence Thomas’ confirmation hearings provides fertile ground for opponents who will likely seek to paint him as too out of touch with the current Democratic Party.

More recently, Biden’s own behavior with women has come under scrutiny as well. After a former Democratic candidate for lieutenant governor in Nevada described feeling deeply uncomfortable when he touched her, kissed her and smelled her hair during a campaign event in 2016, more than half a dozen women came forward to describe similar physical interactions.

Biden responded to the allegations in a cell phone video, saying that he would be more “mindful” of women’s personal space in the future, but later joked about the controversy, a sign that the former vice president’s famously undisciplined speaking style, too, presents potential pitfalls.

But Biden’s strong relationship with white working-class voters, a cohort that Democrats are desperate to win back from Trump in the coming election, combined with his close ties with Obama-era fundraisers and staffers will make for a formidable campaign operation—even in a field of 21 candidates.