Why President Obama's Campaign Blitz for Hillary Clinton Is Historic President Obama's campaign blitz for Hillary Clinton is historic.

 -- As he barnstorms swing states in the closing days of the 2016 race, President Obama is forging an unprecedented final campaign for an outgoing incumbent president not seen in the modern age -- and a move that could help tip the scale in Hillary Clinton's favor.

Obama is spending every day this week crisscrossing the map to stump for Clinton in key battleground states, and her campaign is capitalizing on his strong approval numbers, which are the highest they’ve been since the early days of his presidency. A recent ABC News/Washington Post poll put his approval rating at 58 percent.

“There’s a reason that Secretary Clinton’s team has asked President Obama to maintain such an aggressive travel schedule,” White House press secretary Josh Earnest said Tuesday as Obama set out on his final campaign blitz in the week before Election Day. “They believe that he is a particularly effective messenger in making the case for Secretary Clinton to the American people.”

Obama is spending two days this week in the battleground of North Carolina and making stops in the swing states of Florida and Ohio.

Just how unusual is it for outgoing presidents to be central surrogates for their party’s nominees? It’s unparalleled in modern U.S. history.

One factor is that most outgoing two-term presidents lack the political capital to bestow on their party’s nominees.

In 2008, for instance, President George W. Bush, with his sagging approval numbers, was more of a liability than an asset to candidate John McCain. During the campaign, Bush’s role was reserved almost exclusively for fundraising in private for McCain.

And in 2000, even though President Bill Clinton had a solid approval rating above the 50 percent mark, his personal scandals kept him sidelined from a prominent role in then–Vice President Al Gore’s campaign. That decision by the Gore campaign is now seen as a strategic blunder, says George Mason University political science professor Jeremy Mayer.

“Gore stiff-armed Clinton, and many analysts say that’s one of the factors that led to Gore’s defeat and that had Gore gotten that great campaigner out there, it could have helped him,” Mayer said.

While Bill Clinton did some campaigning for Gore in the final days of the election, he was mostly kept out of the key battleground states.

In 1988, when then–Vice President George H.W. Bush was running to succeed the popular Ronald Reagan, the Bush campaign did not utilize Reagan as Hillary Clinton’s campaign has used Obama, in part because of concerns that the towering Reagan might overshadow the candidate.

“Bush was seen as not as strong or as masculine as Reagan. He needed to establish himself,” Mayer said. “There was a machismo, trying to achieve some machismo.”

“Hillary doesn’t have that problem. Both the president and Michelle [Obama] are more popular than her, but that doesn’t bother her,” Mayer continued.

For Obama, his passionate appeal to voters to elect Clinton is about more than his confidence in his former secretary of state. It’s also about securing his legacy.

“Everything’s we’ve done is dependent on me being able to pass the baton to someone who believes in the same things I believe in,” Obama said in a radio interview taped with Tom Joyner on Tuesday. “So if you really care about my presidency and what we’ve accomplished, then you are going to go and vote.”

Another factor that makes this election personal for the president, Mayer posits, is that he is aware that the Democratic Party has lost control of both chambers of Congress on his watch.

“Obama knows he’s been a disaster for the party outside his presidency,” Mayer said. “It’s not Obama’s fault, but the party below Obama is struggling.”

Beyond stopping Donald Trump from unraveling his agenda, the 2016 campaign is an opportunity for Obama to help restore his party’s strength down the ballot.