Sen. John McCain, the GOP’s presumed presidential nominee, might skip the marquee President’s Dinner next month because of a scheduling conflict, missing an opportunity to showcase the party’s top-to-bottom unity for the 2008 ticket.

The Arizona Senator has other commitments and has yet to confirm his attendance at the June 18 dinner — the biggest annual fundraising event benefiting Congressional Republicans. Aides said the scheduling conflict is the reason and dismissed the idea that he is distancing himself from an unpopular president.

Sen. Orrin Hatch (R-Utah), who is Senate chairman of the dinner, said Wednesday that while McCain’s presence would help boost Republican coffers, he wouldn’t see his absence as a slight.

“I have asked him if he can rearrange his schedule, and I hope he can,” Hatch said. “I want him there. But I understand he has a pre-arrangement and has prior commitments. I want him to do what’s best for him.”

Still, Hatch sounded doubtful that McCain will be able to attend.

Rep. Jeb Hensarling (Texas), the House chairman of the dinner, said similarly that it is his understanding that McCain’s campaign is working on the scheduling issue.

“I’m under the impression he’s trying to work it out in his schedule,” Hensarling said.

The dinner at the Washington Convention Center has a goal of raising $7 million for the National Republican Congressional Committee and $12 million for the National Republican Senatorial Committee.

McCain has events scheduled in three states on June 18, beginning in Texas and including stops in Missouri and Chicago.

A source close to the campaign said McCain’s long-standing commitments are crucial to an organization that is working overtime to fill its war chest against a powerful Democratic fundraising machine.

McCain doesn’t want to double up his efforts, especially since Bush will be headlining the 2008 House and Senate fundraising event.

“It just makes sense for him be on the road doing what he can to get his message out if we already have a great draw and a good motivator” in Bush, the source said.

Many in the party were hoping the dinner would showcase unity with their presidential nominee and also serve as a passing of the party’s standard-bearer baton from Bush to McCain.

The Arizona Senator’s absence would also come at a time when many in the party are discussing ways they can distance themselves from the president and attach themselves to McCain. Some strategists argue that a break from the president is one of the few tactics available to help salvage the party from catastrophic losses downballot in November. The source close to McCain dismissed the idea that McCain has political motivations for skipping the dinner.

“We’re not running away from anybody,” the source said. “It is duplicative. We want to help our House and Senate colleagues. We are meeting with our Hill colleagues all the time. But we’ve been underfunded. We are vacuuming up all the money we can.”

NRCC Chairman Tom Cole (Okla.) said it would be surprising for the party’s presidential candidate to attend.

“I wouldn’t expect him there,” Cole said. “It’s not his dinner. It’s the President’s Dinner.”

Cole also said that Bush remains enormously popular with the party’s donor base and that there would be no reason for McCain to distance himself from the event.

“I’ve got a lot more requests for the president than I have presidential time,” Cole said.

Fundraising for the dinner appears to be on track despite the recent hit in Republican morale after defeats in three special House elections this year.

Hensarling said the special election losses were a wake-up call and will be helpful, not hurtful, to the President’s Dinner’s bottom line as members see the GOP needs “more ammunition to send to the front line.”

He said the dinner has gotten off to a good start, bringing in twice the amount of early money that the dinner did last year.

“We have two choices, crawl into the fetal position or fight,” Hensarling said, “and most of our people have chosen to fight.”

Still, one GOP lobbyist acknowledged the uphill financial situation facing the party.

“My companies are just reading the tea leaves and wondering why do I keep giving to Republicans,” said the lobbyist, who is not involved in the dinner. “It’s not because of the issues; it’s because people see that they’re not going to be in power for a long time.”

Regardless of whether McCain can attend, Hatch said the dinner “will be successful, no matter what.”

Steven T. Dennis contributed to this report.