Among those who will not attend are Sen. Ted Stevens of Alaska, who is not close to presumptive presidential nominee Sen. John McCain of Arizona, and Sen. Susan Collins of Maine, who is a McCain loyalist. Stevens and Collins will use the convention week to focus on their campaigns.
Also sending regrets is former Rep. Bob Schaffer of Colorado, running for the seat being vacated by retiring GOP Sen. Wayne Allard.
Six others -- Sens. Roger Wicker of Mississippi, John Sununu of New Hampshire, Elizabeth Dole of North Carolina and Gordon Smith of Oregon and challengers John Kennedy of Louisiana and Rep. Steve Pearce of New Mexico are still on the fence. Their spokesman offered responses ranging from "there are no plans yet" to "no decisions have been made."
By contrast, most Democrats in those races are either planning to attend the party's late August convention in Denver or are leaning toward attending the event that will formally make Sen. Barack Obama of Illinois the party's nominee for president.
The Republican convention will be bookended by speeches from President Bush, whose low approval ratings have caused many candidates to keep him at arm's length, and McCain, who is still trying to mend fences with conservatives. But none of the absentees or potential no-shows is publicly citing Bush or McCain as the reason for their decisions.
Instead, they and their campaign aides point to the difficult campaign landscape and limited opportunities to campaign.
Stevens, for example, is focusing on Alaska's Aug. 26 primary, which will take place during the Democratic convention, and will stay at home to campaign the following week when Republicans gather to anoint McCain. Because of the timing of the primary, Democratic candidate Mark Begich, the mayor of Anchorage, will also miss his party's convention.
Collins will spend the week campaigning, said spokesman Kevin Kelley. Her opponent, Rep. Tom Allen, will be in Denver. Asked if Allen would attend, speak or raise funds at the Democratic gathering, spokeswoman Carol Andrews replied, "Yes, yes and yes."
And while Schaffer eschews Minnesota to campaign in Colorado, his Democratic foe for the Senate seat, Rep. Mark Udall, can keep campaigning while attending his party's convention, since it is in his home state.
Kennedy's opponent in Louisiana, Sen. Mary Landrieu, is bound for Denver, as are Oregon House Speaker Jeff Merkley; Sununu's challenger, former New Hampshire Gov. Jeanne Shaheen; and Pearce's foe, Rep. Tom Udall.
While Wicker, the newest senator, has not officially sent regrets, his opponent, former Mississippi Gov. Ronnie Musgrove, is definitely staying away from Denver. "He's not a delegate or an alternate delegate, and it's more important for him to spend the time in the state campaigning," a spokesman said.
Dole's Democratic challenger, Kay Hagan, has not committed to attending the Denver convention, but an aide said the campaign has discussed the possibility of a brief stay.
So who among the top targeted Republicans is going to St. Paul?
For starters, Senate Minority Leader McConnell will be there, as will Sen. Norm Coleman, who pushed to bring the GOP bash to his home state. His campaign is already promoting a fundraiser at nearby bar for 40 convention attendees under the age of 40.
Coleman's likely Democratic opponent, Al Franken, does not know whether he'll head to Denver. Spokeswoman Jess McIntosh noted that the convention comes right in the middle of the Minnesota State Fair - a key opportunity to campaign. But, she said, "We're thrilled to stand with Sen. Obama, and we're trying to work out a time when Al can come out to Denver and be a part of history. But plans are not finalized yet."
There is at least one state that will send both Senate candidates to their respective conventions -- Virginia. Both former Govs. Jim Gilmore, a Republican, and Mark Warner, a Democrat, plan to spend at least some time at the conventions.