Speaking at a firefighters' conference Tuesday, former vice president Joe Biden didn't leave much doubt that he'll be running for president. "I appreciate the energy you showed when I got up here. Save it a little longer, I may need it in a few weeks," he said after a raucous welcome. He added, "Be careful what you wish for." His appearance reminds us of why he could be formidable.

First, if Sen. Bernie Sanders, I-Vt., wants to fundamentally change the United States ("Socialism!" Republicans will scream) and Sen. Elizabeth Warren, D-Mass., says the system is so rigged that incremental changes won't work, Biden appeals to Americans' better angels, to the idea that President Donald Trump doesn't understand what makes America great. "That's not who we are," Biden says after describing the divisiveness and anger that Trump amplifies. "We're better than that," he cajoles the crowd. It's a solid message for a candidate running in a fairly good economy with a president who's stressing out the country. He also suggests a confidence of America post-Trump. ("There is nothing we can't do," Biden likes to say.)

Second, there are few politicians as adept at making a traditional economic message against stereotypical fat-cat Republicans. "I look around this room, I see the people who built this nation," he told the crowd. And boy, have Republicans given him material to work with. He told the firefighters, "Did you see the budget that was just introduced? It cuts $845 billion . . . in Medicare and . . . $240 billion in Medicaid. Why? Because of a tax cut for the super-wealthy that created a deficit of $1.9 trillion and now they've got to make somebody pay for it." Bingo.

Any presidential candidate who isn't saying some variation of that every day is foolish. This is where you remind voters that Trump ran as a populist - better health care, middle-class tax relief, protect Medicare, get better trade deals - but governs as an oligarch - take away Obamacare, increase the gap between rich and everyone else with tax cuts for him and his pals, slash Medicare and get us into trade wars.

Three, Biden's speech is suitable for all audiences become he talks about core values. ("America is an idea, an idea that goes back to our founding.") It's "corny" he says - and then recites the opening of the Declaration of Independence. If Sanders, Warren and others are narrowcasting to a segment of the party, Biden is quite consciously talking to the party as a whole and implicitly promising to unify two wings of the party.

Fourth, Biden is best when he talks deliberately, softly. In contrast to the rash, impulsive, insulting rhetoric we hear from a bellowing president, Biden comes across, when he is in quiet mode, as calm, in control and stable. Now, those are not three adjectives one always associates with Biden. However, he is capable of projecting that persona, and in a field of screamers and candidates in love with their own poetic turns of phrase, his direct, simple declarative statements do make him seem more grounded in the real world.

Finally, while he is the veteran politician in the crowd, he can be forward-looking and aspirational. "In America, everybody gets a shot," Biden said. "That's what the next president of the United States needs to understand. That's what I don't think this current president understands at all."

A land of opportunity. The American Dream. Especially to older voters (some of whom voted for Trump), this sounds reassuring; to younger voters, it's a response to the fear that they'll do worse off than their parents. In contrast to a president who constantly stirs up fear, resentment and anger, Biden is offering a simple but alluring commodity: hope.