INDIANAPOLIS (AP) — Republicans said Thursday they were confident presidential candidate John McCain has enough petition signatures to appear on the Indiana primary ballot despite a challenge filed by the operator of a liberal Internet site.

The challenge claims the McCain petitions filed Feb. 12 with the Indiana secretary of state's office did not have the required 500 signatures from each of the state's nine congressional districts.

Indiana Republican spokesman Jay Kenworthy said he checked the McCain petition on Thursday and counted 531 signatures from the 4th Congressional District, the one in question.

"It is a completely bogus charge from the Democrats and their surrogates," Kenworthy said.

State Democratic Chairman Dan Parker, however, said a member of his staff counted 496 signatures from the 4th District.

Brad King, co-director of the Indiana Election Division, said candidates had until noon Friday to make ballot filings and that the agency did not certify the number of signatures submitted unless a petition was challenged.

"There is no official count," he said. "That is determined ultimately by the Election Commission as part of the challenge."

The state Election Commission — made up of two Republicans and two Democrats — has until March 13 to decide on any challenges against primary ballot petitions, King said.

The challenge to McCain was filed Wednesday with the Election Commission by Thomas Cook, an Indiana University student who runs the political blog Blue Indiana.

Cook said he had been checking on candidate filings as part of the political topics on his blog and noticed the McCain shortfall in the heavily Republican 4th District, which covers from the Lafayette area, through the western Indianapolis suburbs to the Bedford area.

Cook said he did not coordinate his challenge to McCain with anyone, although word of its filing was sent to reporters in an e-mail from a Democratic National Committee spokesman.

Indiana Attorney General Steve Carter and state GOP chairman Murray Clark delivered the ballot petition on behalf of McCain, who was scheduled to visit Indianapolis on Friday for a public town hall meeting and a private fundraiser.

Parker said he did not know how the McCain petition could have enough signatures as the deadline for them to be given to county voter registration offices for review was Feb. 12.

"How are they all of a sudden magically getting over 500? That's the question," Parker said. "Somebody really should be counting these petitions that people are collecting."

McCain campaign spokesman Brian Rogers said the dispute was an attempt by Democrats to sully the likely Republican presidential nominee.

"This is based on bad numbers," Rogers said. "We're confident that as the process moves forward this all will be cleared up and we'll be on the ballot."