Former President Obama is back on the campaign trail, aiming to boost Democratic candidates — and protect his own legacy.

Obama will be in Florida and Georgia Friday. He’s campaigning with incumbent Sen. Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE (D-Fla.) and gubernatorial candidate Andrew Gillum in Miami, and with Stacey Abrams, who hopes to become America’s first black female governor, in Atlanta.

The reemergence of the most towering figure in the Democratic Party has excited activists who still hanker after a president whose style, as well as politics, is diametrically opposed to President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE’s.

“He is very much my party’s rock star,” said Steve Schale, a well-known Florida strategist who worked on both of Obama’s presidential campaigns, including as state director on the 2008 effort.

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“He is still my party’s most popular public official, and he is one of the guys who has the capability to put together this coalition of independents and swing voters, along with his ability to motivate the base.”

The stakes are very high, and very personal, for Obama.

If Democrats perform poorly on Tuesday, the door will be wide open for Trump to go even further than he already has in dismantling his predecessor’s legacy.

Conversely, if Democrats win control of the House of Representatives, as they are favored to do, it will provide some measure of protection for Obama’s achievements — notably the Affordable Care Act, which has survived GOP efforts to repeal it in full.

"There are a lot of very direct issues on the line, from people's access to health care to economic fairness and more. So the stakes are definitely high,” said Jesse Lehrich, communications director with Organizing for Action, the Obama-aligned group whose roots stretch back to the 2008 campaign.

“If the Democrats get the House back, that is going to prevent the Republicans from doing anything to further erode ObamaCare,” said Bill Carrick, a Los Angeles-based Democratic consultant.

Carrick added that “one of the great storylines coming out of this election is how important health care is to the voters.”

Many Democrats agree, arguing that Republicans have found themselves in a tight spot on the most popular elements of the Affordable Care Act — notably its requirement that insurance companies cover people with pre-existing conditions.

Trump has claimed that he would offer protection on this score, but his administration has joined 20 Republican-led states in a lawsuit that would strike down the entire law, including the preexisting conditions requirement.

Democrats know how potent an issue health care can be. The Affordable Care Act was a huge issue in the 2010 midterm elections, held less than eight months after Obama signed the bill into law. Democrats lost 63 seats in the House and six in the Senate that November.

Now they believe the tide has turned.

ObamaCare “is clearly a powerful asset for Democrats and a big liability for Republicans,” Carrick insisted. “Early on, the Affordable Care Act raised anxiety because there was uncertainty about what it was going to do. As it settles in, it is becoming more popular.”

There are other elements of Obama’s legacy that have already been undone, or that the midterms would do little to protect, however.

A president has greater leeway on foreign policy than domestic policy, and Trump is at least as willing as Obama to test the limits of executive power.

Still, a Democratic majority in at least one chamber of Congress would clearly put a brake on Trump’s agenda. A Democratic sweep — a long-odds bet given the Senate landscape, but not an inconceivable scenario — would magnify that impact even further.

Beyond the specifics of policy, the personal dynamics between Trump and Obama add an additional frisson.

Trump’s original move into the political world was fueled in part by his promotion of the false "birther" theory that Obama was not born in the United States.

He has repeatedly and fiercely criticized his predecessor. But Obama has begun to hit back.

The former president’s engagement in the midterm elections began in earnest with a speech at the University of Illinois-Urbana-Champaign just after Labor Day — one in which he accused Trump of "capitalizing on resentment that politicians have been fanning for years."

At a recent rally in Milwaukee, Obama complained about politicians who he claimed were just “blatantly, repeatedly, baldly, shamelessly lying. Making stuff up.”

He implicitly mocked Trump’s 2016 campaign pledge to “drain the swamp” in Washington as well.

“In Washington they have racked up enough indictments to field a football team,” Obama said. “Nobody in my administration got indicted. So, how is it that they cleaned things up?”

Most polls show Obama to be considerably more popular than Trump.

A NBC News/Wall Street Journal poll conducted in mid-September found that he was viewed favorably by 54 percent of voters and negatively by 32 percent. The same poll found the numbers almost exactly reversed in Trump’s case. The current president was seen positively by 39 percent of voters and unfavorably by 52 percent.

Independent observers say Obama will clearly be a net positive for Democratic candidates because of how beloved he is among the party’s base. But they also caution that his effects should not be overstated, given the current political atmosphere.

“Is it going to help? Yes. Is it going to help a lot? I don’t think so, given the country is so polarized,” said Grant Reeher, a political science professor at Syracuse University. “But it could help get people who would vote Democratic anyway to actually turn up.”

Obama loyalists emphasize that the former president is invested in making sure the next generation of political leaders is diverse — a point that will be underlined by his rallies Friday with Gillum and Abrams, both of whom are black.

In addition to Friday’s events, he will campaign in Gary, Ind., and in his home city of Chicago on Sunday.

Lehrich asserted that "two years of President Trump has only made people long more for the days of the Obama presidency. But I think it was smart of them to save his voice for the final stretch here.”

The key question remains how much of a difference he will make.

The Memo is a reported column by Niall Stanage, primarily focused on Donald Trump’s presidency.