President Obama addresses the nation on Monday night about the reasons for U.S. military involvement in Libya, hoping to reverse early public skepticism about the country’s role in the United Nations’ sanctioned air strikes.

 New data from the Pew Research Center published Monday afternoon show that just under half the public – 47 percent – thinks it was the right decision to conduct military air strikes in Libya. Another 36 percent say it was the wrong decision and 17 percent are unsure.

Further, just 39 percent thinks the United States has a clear goal for taking action in Libya. Even among Democrats, just under half think the air strikes are the right decision or see a clear plan.

 Support for the air strikes is slightly higher among Republicans at 54 percent than it is among Democrats or independents (at 49 and 44 percent, respectively). More than half of Republicans (52 percent) and independents (57 percent) see no clear plan for the engagement, with a relatively high number of Democrats (43 percent) saying the same.

Fully 60 percent in the Pew poll think the military involvement in Libya will last “some time” versus 33 percent who think it will be over pretty quickly. Obama will need to confront these judgments to build the necessary public support to sustain a mission.

 The Pew results on the bombing decision almost exactly match a Gallup poll from a week ago, just days after the bombing commenced on March 19. The Gallup results are noteworthy because at 47 percent approval, it marks the lowest level of initial support in Gallup polls for a variety of U.S. military actions dating back to Grenada in 1983. Pew’s comparisons for initial support in Iraq and Afghanistan at the outset of those conflicts were much higher than for Libya in the current poll.

A deeper review of public data leading up to the United Nations decision to enforce a no-fly zone finds varying levels of support, highly dependent on how the questions were asked. Support has generally been higher when the effort is described as limited in scope and collaborative. Support plummets when any mention of ground troops are put into consideration.

A CBS poll ending March 21 found significantly higher approval than Gallup or Pew at 68 percent for U.S. action with the stipulation that it is “in order to protect civilians from attack by Kaddafi.”

A CNN poll that ended on March 20 found 70 percent in support of establishing a no-fly zone in conjunction with other countries, significantly higher than CNN’s first poll on the topic a week earlier that found 56 percent support.

 Our own Post-ABC poll ending on March 13 found the same level of support as the initial CNN poll, when participants were asked if the U.S. should “participate” in a no-fly zone. But when the question was asked without the “participate” stipulation, support was lower at 49 percent. A Pew poll ending March 13 asked a no-fly zone question among a variety of military options and found 44 percent in favor of action.

Both CNN and Pew’s early polls found lower levels of support when military action is expanded beyond enforcement of a no-fly zone. Just over half, 54 percent, in a CNN poll supported using planes to directly attack Libyan troops. Support sinks to just 28 percent with the prospect of ground troops. Pew’s early poll found similarly lower levels of support for sending arms to anti-government forces, bombing Libyan air defenses or sending ground troops.

This variety of results speaks to Obama’s challenge in defining the extent and limits of involvement in Libya.