President Barack Obama's solid approval ratings on his 100th day in office could help empower him to get big things done.

But the clock is ticking, Michael Wagner says.

"It's fun to make a lot of the first 100 days, but he really has 250 to 300 days" before the inevitable slippage in support is likely to begin, the University of Nebraska-Lincoln political scientist says.

Come about September, there could be a gradual decline, Wagner says.

And if history repeats itself, Obama could lose some of the legislative clout he has now in 2010, when voters could slice into strong Democratic majorities in Congress.

Public support combined with "a unified government" argues for Obama's aggressive pursuit of a comprehensive legislative agenda now, Wagner says.

Sixty-five percent of Americans approve of the president's job performance, as measured by this week's Gallup Poll. That result is comparable to figures in other surveys, which ranged as high as 69 percent in an ABC News/Washington Post poll.

Former President George W. Bush enjoyed 62 percent approval after 100 days in office. He finished his presidency in January with a 34 percent Gallup score after dipping into the 20s for a time.

Wagner, an assistant professor of political science at UNL, focuses on media portrayal and public perceptions as part of his teaching and research on the presidency, elections and campaigns.

The public perception of Obama is positive, Wagner says, but "not terribly surprising" when compared to other presidents in their early months in office.

The media "played a pretty significant role" in legitimizing Obama's candidacy, Wagner says, "but the coverage is not as fawning as Obama's critics say."

What Obama is dealing with now, he says, is the sharp partisan divide that hardened dramatically during Bush's presidency.

"(Bush was) one of the most polarizing presidents" in modern history, Wagner says.

Where Obama has broken through with the public is in process, he says, connecting with people and demonstrating that "change comes from the ground up."

And the new president wins points with the public by reaching out to Republicans in Congress, Wagner says.

Unified Republican opposition to Obama initiatives - not a single Republican House member voted for the president's economic stimulus package - is a political gamble for the GOP, Wagner says.

"If things get better, it's Obama's recovery," he says.

Nevertheless, "if they think these are bad ideas," he says, "they ought to vote no."

Reach Don Walton at 473-7248 or at dwalton@journalstar.com.