In a riff inspired by the blogger Matthew Yglesias a few years ago, I proposed what I called the Green Lantern theory of the presidency to describe people who attribute all policy failures and compromise to a lack of presidential will. (For the uninitiated, the Green Lantern Corps are comic book heroes whose abilities to wield a “power ring” depend on their willpower.)

These assumptions, which come up all the time in political coverage and commentary (and are often encouraged by presidential candidates, particularly before they take office), are now creeping in to reporting and debate on potential policy responses to the elementary school massacre in Newtown, CT.

Many of those sounding Green Lantern-esque notes are advocates of stricter gun control like The Washington Post’s E.J. Dionne, who called on Obama “and the rest of us” to “change the politics of guns,” and New York City Mayor Michael Bloomberg, who said, “It’s time for the president to stand up and lead and tell this country what we should do—not go to Congress and say, ‘What do you guys want to do?”

In other cases, however, reporters have approvingly channeled Green Lantern-style arguments, or raised similar ideas themselves. The New York Times, for instance, recently quoted former Congressional aide Steve Elmendorf stating that, “Nothing’s going to happen here unless Obama decides to put it front and center.” More notably, in a “White House Memo” news analysis piece, the NYT’s Peter Baker acknowledged the political opposition confronting Obama but framed the ”critical choice” facing the president as largely one of resolve:

Should he invest his energy and the stature he won with his re-election last month in a fight he may believe in but is not sure he can actually win? And with his last election now behind him, is he willing or even able to shift the dynamics in Washington to make such fights winnable?

The reality is far from what Green Lanternites might assume. As Ezra Klein recounted in an admirably thorough overview of the political science literature in The New Yorker, the practical powers of the president to change public opinion or pass legislation in Congress are often wildly overstated. The chief executive has some leverage in promoting proposals that are already popular or increasing the salience of certain issues, but policy stalemates in Washington are not easily overcome. Presidential speeches typically fail to change public opinion (as even the “Great Communicator” Ronald Reagan came to understand), and when the president takes a position on an issue before Congress his actions often polarize opposition legislators (as Obama has learned). To take a recent example, George W. Bush tried very hard to sell Social Security private accounts at the beginning of his second term and got nowhere despite enjoying unified GOP control of Congress.

For proposals that require legislative approval (as most significant changes on gun policy would), these limitations on Obama’s presidential influence are compounded by GOP control of the House and the de facto 60-vote requirement to overcome a filibuster in the Senate. Unless the latest tragedy proves to have some extraordinary impact on public opinion (rather than a brief Columbine-style bump), it’s not clear how Obama trying harder or “leading” would force John Boehner and his caucus to offer concessions. (Remember, Republicans already being forced to discuss compromises with Obama over the “fiscal cliff” and debt ceiling, which creates pressure to prove their toughness to conservative activists on other issues.)

To their credit, some journalists have reported these obstacles clearly to their readers. For instance, Michael Crowley’s piece in Time stands out as especially comprehensive among early coverage in noting the GOP’s ability to block legislation in the House and Senate, the divided state of public opinion on gun control, and the likelihood that attention to the issue will fade.

Brendan Nyhan is an assistant professor of government at Dartmouth College. He blogs at brendan-nyhan.com and tweets @BrendanNyhan.