CLEVELAND — A president’s first 100 days are a blur: filling the Cabinet, rushing to deliver on campaign promises before a crisis or adversaries snuff out the honeymoon. The final 100 days are spent protecting the legacy of the last eight years, at least in Barack Obama’s case.

He’s hit the stump hard and often for Hillary Clinton, and more aggressively than any two-term president in years, trying to pave the way for a successor of his party.

“Donald Trump’s closing argument is, ‘What do you have to lose?’ The answer is everything,” Obama warned a crowd of 2,500 at a lakeside rally Friday morning in Cleveland.

“Civility is on the ballot. Tolerance is on the ballot. ... Kindness is on the ballot. All the progress we made the last eight years is on the ballot. Democracy itself is on the ballot.”

History hasn't been kind to two-term presidents seeking to keep their party in control of the White House. Since 1950, it's been done only once in the seven times either party had a shot at a third term in power.

Voters tire after eight years. They clamor for “change” — Obama’s theme in defeating John McCain in 2008 after Texan George W. Bush’s two terms. But it’s not impossible, if the president is popular enough, the economy is humming, and the public feels the country is heading in the right direction. A weak opponent also helps. For Obama, those factors are mostly favorable.

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“It is very difficult for a candidate of a two-term incumbent party president to succeed him,” said William Galston, a top policy adviser in Bill Clinton’s White House. “It does not happen unless the electorate is willing in effect to ratify the performance of the incumbent president. The desire for change is always powerful after eight years, and if the incumbent president can help elect a successor of his own party, then that is a major historical stamp of approval, and what incumbent would not want that?”

Obama's approval rating is hovering around 54 percent, a respectable figure but hardly any guarantee for Democrats. It's similar to Ronald Reagan's at this point in 1988, just before his vice president, George Bush, won the election.

But Bill Clinton’s rating was even higher at this point in 2000, as was Dwight Eisenhower’s in 1960. And both handed off the Oval Office to the other party.

Obama has been stumping for and with Clinton for months, picking up the pace in the final weeks and often speaking of the presidency as a “relay race” in which he wants to pass the baton to a trusted teammate.

"I will consider it a personal insult — an insult to my legacy — if this community lets down its guard and fails to activate itself in this election," he told a Congressional Black Caucus gala a month ago.

What’s at stake

Obama’s vigorous use of executive authority makes the threat to his legacy very real.

In 2010, he ordered an end to deportations of people brought to the country illegally as youths. In 2015, courts — prodded by Texas and other states — stymied his effort to expand the protection to parents and other relatives of U.S. citizens.

A future president could shred such orders on Day One, as Trump — echoing other Republicans who sought the presidency this year, including Sen. Ted Cruz of Texas — has vowed to do.

“When Obama says his legacy is on the line, he is not speaking hyperbolically. An enormous portion of his legacy is subject to attack or outright reversal” by the next president, said Galston, a senior fellow at the left-leaning Brookings Institution. “This is a game with very high stakes.”

President Barack Obama greeted the crowd after speaking at a campaign event for the Ohio Democratic Party at the Greater Columbus Convention Center on Thursday. (Susan Walsh/The Associated Press)

Two major pieces of legislation are also on the line: the Dodd-Frank financial regulations law and the Affordable Care Act. That’s especially true if Republicans keep control of the House and Senate.

Had Obama lost his re-election and with it, the power of the veto, Obamacare might already be dead.

Immigration policy isn't the only area in which Obama has flexed executive muscle. A president's control over foreign policy is vast. The deal he cut with Iran, lifting sanctions and halting its nuclear program, could be undone. So could the opening with Cuba after a half-century of animosity.

On trade, Obama’s push for a major trans-Pacific free trade deal faces uncertain prospects. Under pressure from the left during the primaries, Clinton promised to reject it, though she advocated the deal as secretary of state. Supporters of the deal hope she softens and finds a way to tweak it enough to save face and embrace it.

Trump would halt trade liberalization efforts. He might withdraw the U.S. from the partnership forged with Mexico and Canada under George H.W. Bush and ratified under Bill Clinton. He would antagonize Mexico by building a border wall and then trying to coerce Mexico to pay for it.

Obama projects a keen sense that his legacy and agenda are on the line.

“I will not be on the ballot, but everything we've done is going to be on the ballot,” he said at an Ohio Democratic Party dinner Thursday night in Columbus. He repeated the point for emphasis. “I'm not going to be on the ballot, but all the progress that we've made, all that stuff goes out the window if we don't work as hard as we can to win this election.”

And then there’s the stylistic contrast should Trump succeed Obama.

The president is reserved, academic, civil. The Republican nominee is bombastic, vulgar, theatrical. Obama’s accusers say he’s divisive. Trump’s can point to explicit rhetoric painting Mexicans as rapists and murderers.

“You can reject a politics of fear and resentment and blame and anger and hate,” Obama told the Cleveland crowd Friday.

History unkind to third terms

Democrats lost four of the last five times they sought a third term — most recently in 2000, when Vice President Al Gore won the popular vote but lost in the electoral tally. Franklin D. Roosevelt was the last Democrat to extend the party’s control beyond eight years, and that was in 1940, when he won an unprecedented third term before the constitutional amendment precluding such longevity in office.

Republicans also struggle. Before the elder Bush in 1988, Teddy Roosevelt succeeded a fellow Republican after two terms in 1904. But Richard Nixon failed in 1960. So did Gerald Ford in 1976 and McCain in 2008.

Conservatives, of course, would be happy to toss aside the Obama legacy. They view him as a closet socialist who seeks the redistribution of wealth through the tax code and by other means and as an internationalist who has hollowed out the U.S. military and left American prestige and power battered.

Campaigner in chief

What Obama is attempting isn’t easy. But it’s obvious why he’s trying.

“The core of the Obama philosophy is really at stake. It’s more than just policy items here and there. It’s the vision of progressive governance that he established over the last eight years,” said Lanhee Chen, chief policy adviser to Republican Mitt Romney’s presidential campaign in 2012 and an adviser to Sen. Marco Rubio’s campaign this year.

The embodiment of that is Obamacare, with the prospect of its repeal or evisceration a high concern to Obama and those around him.

Chen also pointed to financial regulation, the direction of the tax system and Supreme Court vacancies.

“I would see [Clinton] as an extension of Obama — Obama’s third term, but hopefully with some practical streaks thrown in that will permit working with Republicans when it makes sense,” said Chen, director of public policy studies at Stanford University.

Obama’s eagerness to campaign for Clinton stems not only from his desire to protect his policy agenda. It’s apparent at his rallies that he’s in his element. He likes campaigning. And his relatively strong approval ratings put him in a good position to help — though he can thank the deeply unpopular Trump and Clinton.

“I don’t think they’re running a particularly more effective political operation or a better White House,” Chen said. “People look at their alternatives and they feel like vomiting."