After criticism, slide in polls following first debate, is Walker making changes on campaign trail?

SIMI VALLEY, California -- The second Republican presidential debate is set for September 16th at the Ronald Reagan Presidential Library in Simi Valley, California. The debate will air on CNN, and similar to the first FOX News-sponsored debate in Cleveland, Ohio, it will be split into primetime and pre-primetime groups based on averaged polling numbers.

The primetime group will consist of no more than 10 candidates.

Scott Walker at first GOP presidential debate in Cleveland

Some have called Governor Scott Walker's performance in the first debate in Cleveland lackluster -- so has that criticism and the rise of Donald Trump, who is now the GOP front-runner, inspired Walker to reinvent himself on the campaign trail?

Following the first GOP presidential debate on August 6th, Walker has seen his support slip in some polls.

But when it comes to presidential politics, it can be best to think of the race for the White House like the stock market.

"It goes up. It goes down. It can be volatile," Mordecai Lee, a professor at UW-Milwaukee said.

Public opinion polls can be a bit like a "bear" or "bull" market too.

Suffolk University poll

Governor Walker, an early favorite, has fallen in the polls following the first presidential debate.

"The myth has grown since the evening of the debate. The evening of the debate he wasn't that impressive, but he didn't have any gaffes," Lee said.

Lee says pundits' assessments of Walker's performance in that first debate have gotten harsher.

Scott Walker

"They went from unimpressive, to free fall, to weak, to fading in the polls, to not showing that he's got it -- and it's just been amazing how the narrative has changed," Lee said.

That's why it may feel as though Walker has been tweaking his tone a bit lately on the campaign trail.

"Politics is branding. He's trying to change his game a little bit and be a little stronger -- be more in control of his own image and not let others define who he is," Brian Bennett with STIR Marketing said.

Walker has also been sharing his policies as it relates to the hot topics in this race, such as immigration and foreign policy -- speaking out against President Barack Obama's proposed nuclear deal with Iran, and telling voters if he is elected, the U.S. would aggressively confront “radical Islamic terrorism."

Gov. Scott Walker on the political soapbox at the Iowa State Fair

"There's a lot of things that any brand really needs to do in order to be successful, right? You need to be top of mind. So that speaks to the way he's coming out with position papers. He wants to be in front of the news," Bennett said.

Lee says he thinks Walker is fine tuning his campaign -- but says he's not throwing the play book out the window.

"There's no doubt that in the last couple of weeks he's tried to show a little more heat, a little more passion, a little more detail, but I don't think he's changing very much," Lee said.

Another thing to keep in mind when it comes to the latest polls, Lee says door-to-door retail campaigning tends to work well with Iowa caucus-goers, and he says that style of campaigning is one of Governor Walker's strengths.