President Obama will deliver his State of the Union address tonight and will reportedly unveil a new slogan: “win the future” is out; “built to last” is in.

One of the larger questions, of course, is whether the speech will matter. Can we expect Obama to get a bump in the polls? Probably not. The post-SOTU bounce is largely mythical. Can we expect Congress to take the president’s vision seriously as the basis for a legislative agenda for 2012? Put it this way: very little got done in 2011, and 2012 will almost certainly be worse.

So, why should anyone consider tonight’s speech to a joint session important? Jonathan Bernstein explains why: the SOTU is “usually a reliable guide to White House priorities for the next legislative year and even beyond.”

Students of elections and the presidency have learned that presidents tend to keep their promises, or at least try to, and one way to think about the State of the Union is as a series of promises. Perhaps the most famous one in recent years was George W. Bush’s introduction of the “axis of evil” in the 2002 State of the Union — and with it the fateful pivot from Afghanistan to Iraq. We’re not going to see anything as dramatic this year. But the normal construction of a State of the Union speech involves various outside interests and administration factions fighting to get their priorities mentioned (and as prominently as possible), because they know that it places the president on the path to fighting for those programs. Presidents even wind up searching out new initiatives because they don’t want reporters to conclude that there’s nothing new and that the White House is losing energy; that’s how the Bush administration, for example, wound up supporting a Moon/Mars program.

Even when there appears to be little hope of a cooperative Congress, the specific proposals that the president highlights often matter. Sometimes that’s because the president can move forward on those things without Congressional approval; sometimes it’s because once made, a State of the Union proposal tends to stick around. If Obama is re-elected some of the programs orphaned after this year’s speech may show up during his second term. And of course, proposals can be negative as well: a State of the Union veto threat is a lot less likely to be walked back than one that’s made in a less visible way.

The Monthly‘s Paul Glastris made a similar point on NPR yesterday: “[R]emember, the State of the Union is the blueprint for the government for the next year or, in the case of a re-election year, for the next four years…. So these are marching orders to his government, marching orders to all the people that work for him, marching orders to Democrats throughout the country. ‘Here’s what we want to accomplish. Here are the things we want to do that cohere into a theme and a message. We’ve got a long-term goal here, and in a sense the government will be feeding off that State of the Union for ideas, for formulations for the rest of the year.’”

In other words, if you want to know what Obama’s prepared to fight for, look no further than what he has to say tonight.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.