While Hillary Clinton is off the campaign trail recovering from an acute case of heat stroke chronic dehydration pneumonia flu, the Democrats have deployed their party’s big guns to make up for her absence. President Obama, undoubtedly the biggest of those guns, appeared on the trail for Clinton on Tuesday in Philadelphia, and the significance of his presence was not lost on the press. Broadcast networks, print, and cable news programs noted that the president was coming to Clinton’s rescue as her support in the polls ebbs and amid questions regarding her ethics and health. Given President Obama’s remarkable rebound in his job approval rating polls, it stands to reason his presence on the trail will be a boon for Clinton. But is his popularity transferable?

According to a recent ABC News/Washington Post poll, Barack Obama’s job approval rating now stands at 58 percent. That’s his best rating since the summer of 2009, well before the debate over the passage of the Affordable Care Act sapped both his popularity and that of the party he leads. ABC/WaPo may be a bit of an outlier, but not by much. Three polls taken in as many weeks show Obama’s job approval rating above water by double digits, and the Real Clear Politics average shows the president enjoying the approval of an average of over 51 percent of the public.

Traditionally, the fate of the candidate vying to replace a two-term incumbent of the same party is linked to how voters feel about the outgoing incumbent. Given Obama’s newfound popularity and the fact that her opponent is a controversy magnet, Hillary Clinton’s job should theoretically be fairly achievable. That’s the theory, but it is meeting with some real-world resistance.

There is a hypothesis which holds that Obama’s rebound in the public’s estimation is due in no small part to the unpopularity of both of the major party candidates vying to replace him. The fact that either Hillary Clinton or Donald Trump will become the 45th President of the United States has made the public look more favorably on Obama himself. If so, Hillary Clinton’s popularity and Barack Obama’s are inversely related, and therefore it would be difficult for her to benefit from his presence on the trail.

This will forever remain just a theory. What’s more, it undervalues the impact that economic fundamentals may be having on the mood of the electorate. Even as Hillary Clinton stumbles in the polls and in the streets of Manhattan, the data suggest the public finally has reason to feel like the economic recovery is a real recovery. The labor force is on the rise, including among members of the minority community. For the first time since 2007, household incomes in the United States grew significantly in 2015 (by 5.2 percent). “The figures show how several years of robust employment growth, including 2.4 million people who gained full-time work last year, helped regain ground lost after an especially wrenching downturn, particularly for lower-income households,” the Wall Street Journal reported.

Hillary Clinton may not be hurt by Obama’s presence on the trail, but there’s no indication that she is buoyed by his performance in the years in which she was out of the administration—and she’ll have to do a job to sell people on the idea she should be thought of better because the economy is improving.