The long-shot bid by Republicans to retake control of the Senate is suddenly in play, as the prospect of high-profile Republican candidates entering the fray has pushed the GOP even or ahead in polling for 10 races.

The potential candidacies of former Republican Govs. George E. Pataki in New York and Tommy G. Thompson in Wisconsin are improving the polling fortunes of the party as it pursues seats long in the hands of Democrats, while the anti-government "tea party" movement has provided momentum to Republican challengers in states such as Florida, Arkansas and Pennsylvania.

"If the election were held today, the Republicans could come close to winning back the Senate, if not actually win it," said pollster John Zogby...