President Obama has officially kicked off his re-election bid with a low-key campaign ad designed to stir up the grassroots advocates who helped him win the presidency in 2008. (Watch the video below.) In an email to supporters, Obama said he did not want "expensive TV ads or extravaganzas," but only to start a conversation with ordinary Americans. It's clear that Obama's path back to the White House won't be an easy one. His poll ratings are at a record low, and Republicans have been surging since 2008 — although no clear front-runner has emerged from their presidential pack. Here, a look at six of the key obstacles Obama must overcome to persuade the electorate to give him another four years in charge:

1. Lousy poll numbers

Obama's approval ratings are flat-lining, says Bryan Preston at Pajamas Media. "His job approval rating remains in the 40s and even low 40s." Some polls have him beating a "generic Republican nominee," but "soon enough the nominee won't be generic."

2. A still-struggling economy

Obama will be cheered by the "plummeting" unemployment rate, says James Pethokoukis at Reuters. But he and his team ought to be more concerned about the shrinking of "real disposable personal income." Political scientists agree that income growth, or the lack of it, "is the economic variable with the most impact on national elections." Americans vote with their wallets, and if they seem emptier than usual, "Election Night 2012 could be a long one" for Obama.

3. A less-than-enthusiastic base

Obama's "self-described movement has gradually eroded" since 2008, says Michael Scherer at TIME, and his campaign video is an attempt to "remake the magic." Last time, he was able to rally his troops against the "common foes" of George W. Bush and the Republican establishment. Those foes "are not so evident today." Indeed, Obama's base is so insubstantial "they couldn't even find enough enthusiastic people to fill out a commercial," says Ed Morrissey at Hot Air. Where's the passion? Gone.

4. Suspicions about his patriotism

Obama's foes have made hay out of the suspicion that the president does not share America's moral and religious values, says John Dickerson at Slate. So this video addresses it immediately. "First image: a farm. Second: a church. Third: an American flag." Expect to see more of this kind of thing in future commercials.

5. America's wars

Voters think America is declining as a world power, says Marc Ambinder at National Journal, and want a candidate who will project a muscular, Reaganesque exceptionalism. But Obama has been "boxed in" on Afghanistan, and now has to defend "wars that aren't really wars," such as Libya. All of this will add to the impression that "the young president operates above his actual weight class" as far as foreign policy is concerned.

6. Everything else about his record

One of Obama's main challenges in 2012 will be selling his record to voters, says Michael Muskal at The Los Angeles Times. "Obama will cite health-care insurance overhaul, his administration's response to the recession and his foreign policy, which includes winding down wars in Iraq and Afghanistan." But Republicans can easily cast all three of those as negatives, arguing that his policies are "wrongheaded" and attacking him for a failure of leadership over Libya. Exactly how he will convince voters he has "achieved the changes he has promised" remains to be seen.