JEFFERSON CITY - Less than three weeks before lawmakers meet for their veto session, interest groups are zeroing in on a few senators pivotal to the fate of a concealed-weapons bill.

The groups' strategies include mailing books to senators and rallying religious groups.

Gov. Bob Holden vetoed the bill last month, setting up the showdown at the Sept. 10 veto session. Lawmakers need a two-thirds vote in each chamber to override the veto.

The effort is expected to succeed in the 163-member House, where 109 votes are needed.

The outcome is less certain in the 34-member Senate, so that is where gun-rights advocates and gun-control groups have been concentrating most of their efforts.

The Second Amendment Coalition of Missouri Inc., for example, has given copies of the book The Bias Against Guns to every senator. The group's Web site, like those of other gun-rights organizations, urges people to call their lawmakers about the issue.

Meanwhile, Missouri Impact, a coalition of religious groups that opposes the bill, has been asking churches to discuss the issue with their congregations and contact legislators to oppose the measure. The Missouri Catholic Conference also is asking parishioners to call lawmakers in opposition to the bill.

Both sides concede that getting the 23 votes necessary to override the bill in the Senate will be difficult, even though that is the number of senators who voted for the bill earlier this year.

One senator who voted in favor of the bill, Ken Jacob, a Columbia Democrat, did so strictly for strategic reasons in a failed effort to later kill the measure. Without Jacob's vote, supporters have just 22 votes.

That's where Sen. Michael Gibbons, a Republican from St. Louis County, comes in. Gibbons was the only Republican senator to vote against the bill, and gun-rights advocates hope he will change his vote. The pressure on Gibbons worries gun-control advocates.

"The senator we've been concerned about the most is Mike Gibbons," said Todd Elkins, chairman of Missouri Impact.

Holden held the veto ceremony for the bill in Gibbons' district, a solidly Republican suburban district that overwhelmingly opposed a statewide concealed-weapons referendum in 1999.

Gibbons said the governor was trying to put pressure on him not to favor an override. The senator has said he is re-evaluating his opposition to concealed weapons, adding that he has not seen any evidence that states with similar laws have seen an outbreak of violence.

He has gotten a steady stream of calls and e-mails from supporters and opponents of concealed weapons.

"At this point, there are more people that are contacting me in the hopes that I vote to sustain the governor's veto, but there's a pretty substantial number of people that hope I vote to override," Gibbons said. "For me, in my district, in my party, being pulled very strong in two totally opposite directions, it isn't any fun."

Even with Gibbons' vote, though, there are problems in getting the necessary 23 senators for an override.

Sen. Jon Dolan, a Lake St. Louis Republican who voted in favor of the bill, has been called away for military duty. Dolan, a major in the Army National Guard, said earlier that he would not be able to attend the annual veto session.

Recently, however, there has been talk that Dolan might be able to get temporary leave from his military duties to return for the veto session. Dolan, who is stationed at Fort Carson, Colo., before his unit goes to Guantanamo Bay, Cuba, did not rule out returning.

"When I know that the troops are fine and that the mission is fine, I'll try to make arrangements to get back," he said. "Until that time, there probably remains an 85 percent chance that I will not come back.

"I also have to figure out in my mind if I'm the one true vote. There are a lot of other senators in the mix, and until I'm the one vote, I'm not making a move at all."

Dolan's absence came as a great disappointment to gun-rights groups, who saw this year as their best chance ever of enacting a concealed-carry law.

Dale Schmid, president of the Second Amendment Coalition of Missouri Inc., said the possibility of Dolan's getting leave did not seem likely.

"Other than getting a rowboat and going to Cuba, what can I do?" Schmid said.

Another senator in the mix is Jim Mathewson of Sedalia, one of only four Democrats who voted for the bill. Though he has been a supporter of concealed weapons in the past, Mathewson said he was polling his constituents about the override.

"I am still in the thinking process," Mathewson said when asked how he would vote. "I don't like overriding governors. They take it personal. They make a special list for people who vote against vetoes."

To reach Tim Hoover, Jefferson City reporter, call (573) 634-3565 or send e-mail to thoover@kcstar.com.