President Obama is preparing to announce his big executive action on immigration, possibly as early as this week.

And the earliest indication is that it will be about as popular as he is.

A new poll from USA Today and Princeton Survey Research shows 42 percent approve of Obama acting unilaterally via executive action to address problems in the immigration system. Another 46 percent say Obama should wait for the new GOP-led Congress to pass immigration legislation, while 10 percent are unsure.

The split is somewhat counterintuitive, since a strong majority of Americans approve of creating a path to citizenship for millions of immigrants who are here illegally. As Post pollsters Peyton M. Craighill and Scott Clement pointed out over the weekend, 57 percent of those who voted on Nov. 4 favored legalization for these people, while 39 percent wanted deportation, according to exit polls. And even that split was actually narrower than most polls have shown.

But in politics, the process matters too, and many of those who otherwise support legalization also appear opposed to or hesitant about doing so without the regular checks and balances of the legislative and executive branches. Threading that needle is a difficult exercise for Obama, but he has said Republican leaders have failed to address the issue and now their time is up.

Whatever justification the White House sees, though, it will be a difficult sales job. The devil, after all, is in the details on something like this, and there could be something for everyone to hate. The fact that Americans are pretty lukewarm on the idea of an executive action even before those details come out probably isn't an encouraging sign for the White House.

At the same time, the White House is doing something that, ostensibly, could be popular, and its move to defer deportations for young illegal immigrants in 2012 proved to be a political winner.

But that was a much narrower executive action, and the latest version could potentially defer deportations for millions of illegal immigrants whose immigration history is less sympathetic. There quite simply isn't likely to be the same level of compassion among the American people. And for Americans who favor legalization but aren't that passionate about it -- and they are legion, as evidenced by the lack of impetus in Congress -- an executive action could be a bridge too far.

Finally, as Karen Tumulty and Katie Zezima write in today's Post, the executive action could reach into uncharted territory for a U.S. president on immigration, setting up a showdown in which he dares Congress to stop him.

That's not exactly the recipe for a resounding political success. And if this early poll is any indication, Obama's big executive action is meeting a skeptical public.