CHICAGO – GOP presidential candidates can get an idea of where they stand with Illinois voters during a straw poll on Republican Day at the State Fair in Springfield.

The Illinois Republican Party was sending out invitation letters to the campaigns beginning Wednesday, said spokesman Lance Trover.

Illinois already has moved up the state’s primary to Feb. 5, a move certain to help its Democratic Sen. Barack Obama but one that state GOP party chairman Andy McKenna says also is good for Republicans.

“Illinois will play a central role in choosing the Republican presidential nominee,” McKenna said in a written statement.

As many as 25 states could hold primaries that day, and Illinois joins several delegate-rich states – including California, New York and New Jersey – in settling on the early date.

The GOP field includes former Massachusetts Gov. Mitt Romney, former New York Mayor Rudy Giuliani and Sen. John McCain.

Republican candidates who want to participate in the straw poll have to poll above 5 percent in national, independent polls or have participated in any nationally televised debate this year.

Voting in the Aug. 16 straw poll is open to all eligible Illinois voters who present valid identification to protect against multiple voting.

The poll will be conducted over a five-hour period on the Director’s Lawn at the fairgrounds.