Upstart candidate Rand Paul said a clear-cut victory by him in Kentucky's Republican primary for U.S. Senate would be a strong showing for the tea party movement, which has flexed its muscles already in other races across the country.

The mood of the country and the Republican Party strengthen his position heading into Tuesday's race. He said the outcome will carry clear national implications.

"I think the larger the victory the more the mandate for the tea party," he said.

The tea party movement already helped defeat three-term Sen. Bob Bennett in Utah and forced Florida Gov. Charlie Crist to abandon the GOP to make an independent run for the Senate.

His main rival in the hard-fought Senate primary, Kentucky Secretary of State Trey Grayson, spent the day campaigning in heavily Republican southeastern Kentucky, a region that's expected to be key.

Grayson is backed by Kentucky's most powerful Republican, Senate GOP leader Mitch McConnell. Paul has the backing of Kentucky's other Republican senator, Jim Bunning, who is retiring after two terms.

A political outsider, Paul entered the race as a long shot against Grayson, who has long been considered a rising star in the Kentucky GOP. An antiestablishment mood that swept the country quickly turned the tables in favor of Paul, who leads some polls by double-digits.

Paul, the son of Texas congressman and former GOP presidential candidate Ron Paul, said he has the clear momentum heading into the election.

"The mood of the country is in our favor," Paul said in an interview at his campaign headquarters in his hometown of Bowling Green, where volunteers busily worked the phones. "The mood of the Republican Party is in our favor. The tea party movement is enormous and in our favor. ... Just at every turn everything has gone our way."

Grayson, the state's chief election official, said he isn't convinced polls showing Paul up by double digits are accurate because of dynamics peculiar to Kentucky Republican politics. He said statewide turnout will be only about 30 percent in the primary, which makes regional Republican pockets like southeastern Kentucky key to the outcome.

Turnout in some counties in the region, Grayson said, could be 50 percent to 60 percent because of a large number of local races on the ballots. Southeastern Kentucky, Grayson said, could account for a third of the votes cast in the Senate.

Paul, a small-town eye doctor, attended church with his family in Bowling Green but planned no other public appearances just two days before the election. After months of campaigning, he said he planned to take a relaxing bike ride later in the day if the rainy weather cleared.

He told The Associated Press in an interview, "I'd be very surprised if things didn't go our way on Tuesday."

Grayson also attended church on Sunday. During a fundraiser for a volunteer fire department in Girdler in Knox County, Grayson told the crowd he has the endorsement of two Washington lawmakers who are popular in the region, U.S. Rep. Hal Rogers and McConnell. Both endorsed Grayson over Paul in an unusual and some say divisive move.

Paul has said that he may not support McConnell if he faces opposition for GOP leader in the Senate.

"I'm going to work with Congressman Rogers and Sen. McConnell, not against them," Grayson said Sunday.

In a brief speech, Grayson said that Washington needs to get its "fiscal house in order." Both Grayson and Paul have focused on the need to control federal spending. Paul has gone so far as to call for an end to congressional earmarks, which have been used to fund numerous government programs and projects in Kentucky.

Grayson does not oppose earmarks.

"We need to spend less in Washington, but we need to fight for Kentucky's fair share," he said.

Paul said he's confident he'll have the backing of establishment Republicans heading into the fall campaign.

The two leading Democratic Senate candidates are Lt. Gov. Daniel Mongiardo and state Attorney General Jack Conway, who appeared locked in an agonizingly close race. Mongiardo barely lost to Bunning six years ago.

"I think there will be the ability to work together," Paul said of Kentucky Republicans. "Primaries divide people but general elections bring them back together."

McConnell, during an appearance on NBC's "Meet the Press," predicted that Republicans will rally behind the primary winner. He said Grayson would be a stronger candidate in November but predicted "Kentucky's gonna be in a pretty Republican mood this fall."

McConnell said the tea party has become "an important movement in the country," and said "it's gonna really help us in November."

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Associated Press Writer Roger Alford in southeastern Kentucky contributed to this story.