A new poll shows U.S. presidential candidate Barack Obama leads John McCain in three states that are critical to winning the White House.

The U.S. survey released Wednesday by Quinnipiac University shows that support for Senator Obama jumped to 50 percent or more in the so-called "swing-states" of Ohio, Florida and Pennsylvania.

The poll was taken over the weekend, after Friday's presidential debate and during Monday's spectacular drop in the U.S. stock market.

The survey found an increase in confidence that Senator Obama can handle the economic crisis.  It also credited Obama's widening lead to the Democrat's debate performance and a sagging opinion of his Republican rival's running mate, Alaska Governor Sarah Palin.

Palin is scheduled to debate Obama's running mate, Senator Joe Biden, on Thursday.

Obama and McCain are expected to talk about the economy before returning to Washington Wednesday, for a Senate vote on a bailout plan for the U.S. financial markets.

Senator Obama is scheduled to hold a rally in the northern state of Wisconsin, while Senator McCain is expected to deliver a speech on the economy in the central state of Missouri.

Some information for this report was provided by AFP and AP.