(CNN)Inside Dr. Martin Luther King Jr.'s church in Atlanta on Thursday, the nation's first Black president -- who has acknowledged there was a Black president only because of what John Lewis sacrificed -- delivered a eulogy for the civil rights icon and eventual congressman that went well beyond pure remembrance.In words that were both highly specific and at times more oblique, Obama declared Lewis' lifelong battle for racial equality to be ongoing and stated explicitly that forces in power today are working to undermine it. Drawing a direct line between the bridge in Selma, Alabama, where Lewis was bloodied by state troopers in 1965 and the protests this summer following police killings of Black Americans, Obama delivered his most forceful address since leaving office, casting the actions of his successor -- who avoided any in-person remembrances for Lewis, though three of his four living predecessors made the journey -- as corrosive for democracy. "We may no longer have to guess the number of jelly beans in a jar to cast a ballot, but even as we sit here there are those in power that are doing their darnedest to discourage people from voting," Obama said, hours after President Donald Trump suggested on Twitter that November's presidential contest be delayed because of the unproven potential for fraud. As Trump wages a reelection campaign reliant on racist tropes and a vague notion of "heritage" that many see rooted in an outdated vision of the country, Obama said Lewis would eventually be remembered as another type of national hero. "America was built by John Lewises," Obama said. "He, as much as anyone in our history, brought this country a little bit closer to our highest ideals. And someday, when we do finish that long journey towards freedom, when we do form a more perfect union ... John Lewis will be a founding father of that fuller, fairer, better America."It was a dramatic return to the political fray for a former president who has steadfastly worked to avoid becoming a foil for Trump, even as he frets privately and to Democratic donors about Trump's actions and words. But it was also a deeply personal recognition of a life Obama admitted was necessary for his own political ascent."Imagine the courage of two people Malia's age -- younger than my oldest daughter -- on their own, to challenge an entire infrastructure of oppression," he said, evoking his 22-year-old eldest child. "John was only 20 years old but he pushed all 20 of those years onto the center of the table."At a moment when the country is reckoning anew over questions of systemic racism following the police killings of George Floyd, Breonna Taylor and countless other Black and Brown Americans, Thursday's funeral was a measuring moment: Both a time to reflect on the grainy black-and-white newsreels of another generation's struggle and an opportunity to assess where that struggle continues to come up short. It was the type of remembrance that marks the passage of a nation's history, provides a record of its highest and lowest moments and lays down a marker for the type of person -- the type of hero -- deserving of the country's attention and respect.Lewis' own words kicked off the day of remembrance, with a post-humous op-ed in The New York Times, that echoed the principles with which he lived his life."When you see something that is not right, you must say something. You must do something. Democracy is not a state. It is an act, and each generation must do its part to help build what we called the Beloved Community, a nation and world society at peace with itself," he wrote, recalling his own lessons from King."It is so fitting on the day of his service, he leaves us our marching orders: Keep moving," former President Bill Clinton said during the funeral."He got into a lot of good trouble along the way but let's not forget he also developed an absolutely uncanny ability to heal troubled waters," Clinton added. "He thought that the open hand was better than the clenched fist."While not at all unexpected, the absence Thursday of the sitting president was conspicuous. Remembering heroes was once something Washington could agree on, an idea that has increasingly seemed to be a relic from another time.Lewis' funeral wasn't the first high-profile memorial that Trump has skipped, and as both a lifetime member of the nation's most exclusive club and a renowned grudge-holder, it likely will not be the last.Yet however obvious it was, Trump's decision to forgo paying his respects -- which he declared decisively even before his aides could weigh the pros and cons -- was still a stark reminder of the rabidly polarized era of politics over which he presides.He has continued to stoke a racial divide that Lewis spent his life working to bridge. As the country buckled earlier this summer under racial tensions and outcry over police brutality, Trump harkened back to 1960s rhetoric that wouldn't have been unfamiliar to Lewis, who was beaten and bloodied by police during the civil rights movement.As Trump evoked "vicious dogs" that would restore order and used a phrase coined by a racist police chief in 1968 to warn that "when the looting starts the shooting starts," Lewis encouraged protesters to continue the work that he started decades ago.The comparisons to a darker era that many hoped had faded were made explicit in Obama's eulogy."George Wallace may be gone, but we can witness our federal government sending agents to use tear gas and batons against peaceful demonstrators," he said, referring to the segregationist Alabama governor who ran for president on a hard-right platform in 1968.Even as recently as this week, Trump has used a rollback of a federal anti-segregation rule to appeal to White suburbanites, a tactic that seems to have a direct line to the racist policies Lewis was seeking to overturn half a century ago.It's hard to imagine how those messages or that messenger would have fit in at Lewis' funeral. Yet political leaders have long put aside even their biggest differences to commemorate those few lives that can be said to have altered history. "John and I had our disagreements, of course," former President George W. Bush said during the funeral on Thursday. "But, in the America John Lewis fought for and in the America I believe in, differences of opinion are inevitable elements and evidence of democracy in action."