President Barack Obama clearly leads his Republican rival Mitt Romney in the battleground of Ohio but the race has tightened considerably in two other key states ahead of the November 6 elections, a new poll said Thursday.

Obama continues to enjoy a six-point advantage in Ohio with 50 percent compared to 44 percent for his challenger, according to the Quinnipiac University/CBS News/New York Times poll.

But he is facing increasing competition in Florida, where 49 percent say they would vote for him -- a lead of three points over his opponent that is considered to be within the survey's margin of error.

Romney, at 46 percent, garners more support among men (51 percent compared to 45 percent) and seniors (55 percent compared to 42 percent), a crucial voting group in the so-called Sunshine state.

In Wisconsin, home of Romney's recently announced running mate, congressman Paul Ryan, Obama holds a two-point lead -- also considered within the margin of error -- over his rival with 49 percent, slipping from six points earlier in the month.

While he can claim a nine-point advantage among women, Romney has a five-point edge among men and a large lead among white Catholics (58 percent to 38 percent).

The survey, carried out between August 15-21, shows that the president is seen as better at handling Medicare, a politically sensitive public health program for seniors, than his contender for the White House.