What can May polls say about November?

Updated 5:50 p.m. ET

(CBS News) General election campaigning between Mitt Romney and President Obama is underway, and if history is a guide, polls conducted in the month of May aren't necessarily a predictor of where the race will be in late October. In past years in which an incumbent was running for re-election, the leading candidate in polls conducted around Memorial Day only sometimes came out on top.

In some years, the race changed quite a bit between May and November. For example, a CBS News Poll conducted in late May 2004 found John Kerry leading President George W. Bush by eight points - 49 to 41 percent. President Bush was suffering from growing public concern about the war in Iraq and the prisoner abuse scandals at Abu Ghraib. Kerry led Mr. Bush in most polls until September, but throughout the fall the polls showed a race that was neck and neck. Mr. Bush won re-election by 3 points.

Although President George H. W. Bush's re-election bid was ultimately unsuccessful, he was ahead in the polls in May 1992, beating Bill Clinton by 8 points. President Bush received 35 percent of voters' support, compared to 27 percent for Bill Clinton and 26 percent for Ross Perot in a CBS News Poll.

President Bush's approval rating was the lowest he had ever received up until that point, but voters' views of Bill Clinton were low as well - just 15 percent favorable and 40 percent unfavorable. Throughout the summer, Bill Clinton's support rose steadily; from July onward, Mr. Bush trailed Clinton in the polls

The race could change, in part, because for voters, the presidential race is still months away and most won't focus on the election until the party conventions at the end of the summer.

However, in some elections, May polling reflected a race dynamic that would carry through until November. A CBS News poll from May 1996 showed President Bill Clinton with a lead over Republican challenger Bob Dole, 54 percent to 38 percent. And polls conducted in June 1980 and 1984 were accurate indicators of who would ultimately win those elections. A CBS News/New York Times Poll from June 1980 found challenger Ronald Reagan with a double digit lead over incumbent President Jimmy Carter - 43 percent to just 28 percent for Mr. Carter and 17 percent for John Anderson. Mr. Reagan led challenger Walter Mondale by a large margin in June 1984 as well - 50 percent to 35 percent.

(Watch guests on CBS News' Hotsheet Live program on video below talk about the historical contexts in May polling.)