The results of a survey released Tuesday by polling firm Rasmussen Reports showed U.S. Sen. Barack Obama (D-Ill.) with a slight lead over U.S. Sen. John McCain (R-Ariz.) in the race for Colorado's presidential endorsement.

The poll showed presumptive Democratic presidential nominee Obama with 49 percent support, while his Republican counterpart McCain garnered 42 percent. The 4.5-point margin of error suggested the race could be tighter than the numbers indicate, however, and with so-called leaners included, Obama's lead shrank to three percentage points.

The results come one day after polling firm Zogby International released even closer poll results. Zogby gave Obama a two-point lead, well within the 3.6-point margin of error.

A Rasmussen poll in June showed Obama with a 43-41 lead over McCain; in May it was 48-42 for Obama.

A Democratic victroy in Colorado would be historic. The state has gone to the Democrats just once in the last 40 years, when Bill Clinton defeated George H.W. Bush in 1992.