Ohio voters will be barraged by political polls in the next four months, with up to a dozen released per day, and political experts say the polls are valuable ... if voters know how to use them.

In one 24-hour period June 20-21, five national polls were released on the race for president. Two had former Massachusetts Gov. Mitt Romney leading narrowly (by 2 and 4 points), two had President Barack Obama leading narrowly (by 3 and 4 points) and one had Obama ahead by 13 points.

“The exact wrong thing, which a lot of people do, is they pick the result they like best and rationalize as to why it’s the most reliable,” said Scott Rasmussen, president of the Rasmussen Reports polling agency. “That’s a natural human instinct, but you should always look at as much polling data as you can, and rather than picking apart the differences, look for common ground.”

Recently, four of the five national polls were close — either inside the poll’s stated “margin of error” or within 1 percentage point of it.

“If the ‘registered voter’ polls are showing a little bit of a lead toward Obama and the ‘likely voter’ polls are showing a few points more in Romney’s direction, this race is very close,” Rasmussen said. “That is the overriding message.”

While the campaigns try to use the poll data to their advantage, the pollsters themselves debate how to make their polls as accurate as possible.

Peter Brown, assistant director of the Quinnipiac University Polling Institute, said there are many factors that determine reliability of polls — the number of people questioned, the use of registered voters or likely voters, the effectiveness of human callers vs. computers, and more.

“Everybody is accused of being biased at one time or another,” Brown said. “But we believe our methodology is solid. We believe our questions are written in as impartial a manner as possible. We use human beings to make the calls, which is considered the gold standard. We call cellphones, which is considered the gold standard.”

Rasmussen has been accused by some Democrats of skewing his polls in favor of Republicans. Rasmussen Reports and Gallup Poll are the two organizations that release daily tracking polls on the presidential race. During one stretch, Rasmussen’s results were more favorable to Romney than Gallup’s on 13 of 14 days.

Rasmussen said it’s a sampling issue, as Gallup surveys only registered voters, while Rasmussen uses “likely voters.”

Brown stressed that polls give an accurate snapshot of people’s feelings at one moment in time, adding that the same question asked a week later will likely draw different results. He pointed to 1980 polls showing that Jimmy Carter led eventual winner Ronald Reagan for much of the summer, and 1988 polls where Michael Dukakis was well ahead of George H.W. Bush, as proof of that fluidity.

Pollsters usually do well just before Election Day, when more of the uncertainty has disappeared. A Fordham University survey on the 2008 presidential election showed, on average, 23 major polling agencies missed the Obama-McCain margin by just 1.4 percentage points on their final polls. The final Rasmussen and Pew Research polls were almost exact matches of the national results.