Obama's approval rating is at its highest point in years, and that could be a big problem for Donald Trump

Two years ago, President Barack Obama was largely absent from the campaign trail. Prospective and incumbent senators and members of Congress shied away. His approval rating languished near the lowest point of his presidency.

Two years later, the script has completely flipped. He is trying to help elect the second-least popular nominee in modern presidential history, Hillary Clinton, to carry on his legacy in office. And he's perhaps her best surrogate.

"Obama is the single most effective surrogate she has, and I can't remember a time when an incumbent president this popular campaigned this hard for his party's nominee," said Jon Favreau, the former director of speechwriting for Obama.

Obama hits the trail again Tuesday, when he heads to Philadelphia to campaign for Clinton, as she rests off pneumonia and her campaign looks to turn around a rough past week in her matchup with Republican nominee Donald Trump.

In a new Washington Post poll released over the weekend, the president's approval rating hit an astounding 58%. It's 15 points higher than it was in a Post poll right before the 2014 midterm elections. And it's the highest level since he hit that point six months into his presidency.

"He is the most popular Democrat in the country, and as his term comes toward an end, the intensity of love for him only grows," said Steve Schale, a former Obama campaign state director. "Elect Hillary to protect President Obama's legacy is a very powerful message for Democrats."

The threshold might seem arbitrary. But historical precedent suggests it could bode well for Clinton, Obama's former secretary of state.

Early this year, Obama's approval rating hit 50% in the weekly average from Gallup's daily survey. As of Tuesday, it stands at 51%. For Obama, whose approval ratings have been stuck in the mid- to low-40% range for much of his second term, it was a notable bump.

"While it's hard to pinpoint precisely why Obama's approval rating has risen among Democrats recently, there are a number of plausible explanations," wrote Andrew Dugan, a Gallup analyst, and Frank Newport, the organization's editor-in-chief, in a post earlier this year.

One of the explanations, the pair concurred, was that "the unusual status of the Republican primary race - exemplified in particular by frontrunner Donald Trump's campaign style and rhetoric - may serve to make Obama look statesmanlike in comparison."

"He reminds swing voters of the basic decency they miss in politics," Schale said. "I believe a lot of the increase in his popularity of late has to do with a visceral reaction to the abrasive vitriol of Trump. They see Obama as measured and thoughtful, dare I say with the right kind of temperament to hold the rudder of a nation through the troubled global waters. His style creates an inherent contrast with Trump, and it is a contrast that benefits Clinton."

Trump has come into Obama's crosshairs repeatedly as he has hit the trail for Clinton. And with good reason: More so than at any other presidential hand-off in recent history, so many elements of the current administration's legacy are at stake.

The Republican nominee has pledged to undo signature achievements on healthcare (the Affordable Care Act), the environment (historic new regulations aimed at curbing climate change), and foreign policy (the Iran nuclear deal).

Trump has sought to frame Obama's tenure as a disaster. But the president's spiking approval ratings and popularity suggest that argument might become more and more lost on swing-state voters.

"A lot of Republican are misjudging the fact that despite most of the country thinking the nation is on the wrong track, swing voters have a more favorable than unfavorable view of Obama," said Tim Miller, a former spokesman for Jeb Bush's presidential campaign who has been critical of Trump.

"So Republicans in swing states are succeeding - Rob Portman, Joe Heck, Marco [Rubio] - when they highlight their independence and their desire to roll back government policies like Obamacare that are unpopular," he added. "But when Trump claims that Obama is an un-American disaster, that might play on talk radio but it isn't how voters who will decide this election view the world."

Said Favreau: "Trump has convinced himself that the Fox News view of Obama is the public's view, so I hope he keeps making the third-term argument."

Obama's approval ratings at this point are far better than those of President George W. Bush, his predecessor, off whose unpopularity Obama thrived during his 2008 run. His level is most directly comparable to former President Ronald Reagan, who in March 1988 held a 51% approval rating, according to Gallup.

That same year, voters selected George H.W. Bush - Reagan's vice president - to succeed him.

"Yes," said Ari Fleischer, President George W. Bush's former press secretary, when asked earlier this year if Obama's apparent rising popularity poses a problem for the Republican Party.

"Certainly, going into an election spring and summer, it's better to have an incumbent president increasingly popular rather than less popular if you're the incumbent party," he told Business Insider.

The numbers present a striking contrast to some data points associated with the current Republican presidential nominee.

A Gallup survey earlier this year revealed that 42% of voters view Trump in a "highly unfavorable" light, compared with 16% who see him highly favorably. That's the highest negative percentage for any major presidential candidate since at least 1956, according to Gallup.

"I've been doing this [since] 1964, which is the Goldwater years," NBC/WSJ co-pollster Peter Hart told NBC earlier this year of the relative unpopularity of many of the candidates earlier in the year. "To me, this is the low point. I've seen the disgust and the polarization. Never, never seen anything like this. They're not going up; they're going down."

Closest to Trump? Clinton, whom 33% of the electorate views highly unfavorably.

It helps explain why Clinton is attaching herself to much of Obama's legacy. And Obama remains favorable to wide swaths of constituencies that Clinton needs to turn out to vote in November. The president holds high approval ratings among African-Americans (90%), Democrats (82%), Latinos (73%), and voters aged 18 to 34 (64%), according to Gallup.

"You can't recreate the Obama coalition - she has to build a Hillary coalition," Schale said. "But nonetheless, the president is a motivator, particularly for African American voters."