INDIANAPOLIS (AP) — Former Republican Sen. Dan Coats' campaign said Tuesday it has more than enough petition signatures to put him on Indiana's May primary ballot as he seeks the Senate seat Democrat Evan Bayh is leaving.

Coats won't have a clear path to his party's nomination, as at least four other Republicans expect to be on the ballot. Meanwhile, no Democrats met Tuesday's deadline to submit the necessary signatures to get on the primary ballot, meaning state party officials will pick a candidate for the November election.

Coats spokesman Kevin Kellems said Hoosiers had responded with "tremendous enthusiasm" in helping gather the required 4,500 signatures since Coats announced his campaign on Feb. 3.

Coats, 66, spent 10 years in the Senate but did not seek re-election in 1998, avoiding a contest against Bayh. He said in an interview last week that as a former senator he was in the best position among the Republicans seeking the nomination to wage a formidable campaign against Bayh.

Kellems said Tuesday that Coats would run just as hard even with Bayh out of the race and was taking nothing for granted.

"Many Democrat political pros and the White House see this race as a factor in maintaining control of the U.S. Senate to protect the president's extreme political agenda, and therefore will field and finance a very strong campaign," Kellems said.

Of the other four seeking the Republican nomination, former Rep. John Hostettler said he also had enough signatures, as did state Sen. Marlin Stutzman of Howe, who filed for the primary Tuesday. Financial adviser Don Bates Jr. of Winchester filed last week for the GOP primary.

A spokesman for Fishers businessman Richard Behney said he also had enough signatures to get on the ballot.

Stutzman said Tuesday he had traveled the state for more than 18,000 miles over the past several months laying a foundation for his campaign. He predicted that Republicans would not be fractured after the May 4 primary.

"I think once we get through the primary, we're going to work hard and come together to elect a Republican to the U.S. Senate," Stutzman said.

The 32 members of the state Democratic central committee will select their party's nominee after the only Democrat seeking to run for the Senate seat missed out on qualifying for the primary ballot.

State Democratic chairman Dan Parker said Bloomington cafe owner Tamyra d'Ippolito failed to submit the needed 500 signatures in the 7th District. The Marion County voter registration office reports it received just three signatures for her by Tuesday's deadline.

In Indiana, candidates for U.S. Senate must submit 500 certified signatures in each of the state's nine congressional districts to qualify for the primary ballot.

Democratic leaders will have until June 30 to fill the spot, and Parker said the central committee will not call a meeting until there's consensus for the party's eventual choice.

Bayh stunned political circles when he announced Monday that he would not seek a third term this year. He attributed his decision to the bitter partisan divides that have dominated Congress in recent years.

Bayh, 54, said he believed he would have been re-elected this November, despite "the current challenging environment." But he said it was time for him to contribute to society in another way, either by creating jobs with a business, leading a college or university, or running a charity.

He had until recent weeks been regarded as a near certainty for re-election, having raised nearly $13 million for his campaign and facing little-known Republican opposition until national Republicans recruited Coats to enter the race.

Bayh has not said what he will do with his campaign money.

Christian Hilland, a spokesman for the Federal Election Commission, said Bayh had to refund more than $570,000 he received that is earmarked specifically for the 2010 general election. Of the rest, he can spend $2,000 in the primary and again on the general election for individual federal candidates.

He can transfer as much as he wants to the Democratic National Committee, the Democratic Congressional Campaign Committee or the Democratic Senate Campaign Committee, and can give money to the Indiana Democratic Party, Hilland said.