When President Barack Obama addresses the nation from the U.S. House today, he will do more than report on the state of the union. He also will signal the type of Democrat he will be for the rest of his term.

The president showed in Tucson that he has fully stepped into the role of head of state. But when it comes to being head of our government, it’s unclear what the next two years portend.

So far, Obama has been a pragmatic liberal. Think of him as a modern Ted Kennedy, who stood to the left of Democrats like Bill Clinton, Jimmy Carter and Paul Tsongas, another Massachusetts senator. But like Kennedy, Obama recently has shown a willingness to temporarily back off his ideals and compromise. The tax package he recently accepted, which extended all the Bush-era tax cuts, was reminiscent of Kennedy accepting parts of education or health care bills that he didn’t like so he could get what he did like.

But being a pragmatic liberal is different from being a modernizer of the Democratic Party, which was the driving passion of reformers like Clinton and Tsongas. They birthed the New Democratic movement of the 1990s. Obama seems interested in modernizing our discourse so it will be more civil. For that we should be glad. But rarely has he seemed interested in recasting the Democratic Party.

Instead, he largely embraced a stimulus package crafted by House liberals, bowed to unions on a key financing element of the health care bill and alienated the business community on numerous fronts. Except for his education and Afghanistan policies and, more recently, trade negotiations, he has not rooted himself in the center, where Clinton and Tsongas tried to locate the party.

Obama’s course until now might make sense because his journey to power is more that of a traditional liberal. Journalist Edward McClelland superbly captures that rise in his new book, “Young Mr. Obama: Chicago and the Making of a Black President.” Little in his description of Obama’s work in the 1990s as a community organizer, state senator and congressional hopeful gives you the sense that the up-and-comer was a product of the New Democratic movement.

Liberalism was being recast abroad at the time, too. I’ve been reading Tony Blair’s autobiography alongside “Young Mr. Obama,” and the contrast is sharp. Page after page, the former British prime minister describes his battles against his own Labor Party colleagues who could not understand that a shift was under way between the power of the state and that of the individual. At most every turn, Blair prompted his center-left party to adjust to that shift. It’s hard to say that about Obama‘s first two years as president.

Yes, Obama has just picked a Democratic centrist, business executive William Daley, to head his staff. But we don’t know if that is a tactical move to get an executive to run his administration or a philosophical one that suggests he will spend the next two years building coalitions from the center out.

The country will win if he takes the latter course. The battle over the deficit and debt will require Obama to build a coalition that will reform entitlements, overhaul the tax code and cut prized programs.

Washington also needs a coalition to update No Child Left Behind. Obama has shown the guts of a Democratic modernizer when it comes to issues like shutting down bad schools. Students will gain if he remains the modernizer.

Obama will be the major winner if he plays the reformer, not the pragmatic liberal. The independents who helped elect him in 2008 left Democrats in droves in November. Getting them back in 2012 will require a more centrist approach.

We will see if he intends to do that once he steps onto the floor of the House of Representatives today.

William McKenzie is an editorial columnist for the Dallas Morning News.