NASHVILLE, Tenn. — If Republicans lose control of Congress, the Supreme Court will be packed with abortion-backing liberals, tax dollars will pay for research on cloning to create “little human beings” for organ farming, and elementary school teachers will be forced to promote homosexuality to their students.

That’s the view and vision of James Dobson, chairman of Focus on the Family, a nationwide, politically active evangelical group allied with the Republican Party. The moral future of America is at stake and “staying home” isn’t an option, Mr. Dobson told 2,400 followers at an October 16 get-out-thevote rally at the Two Rivers Baptist Church in Nashville. “Folks, we cannot afford to do that.”

A big turnout among evangelical Christians helped a White House adviser, Karl Rove, secure President Bush’s re-election and the Republicans’ increased congressional majority in 2004. The effort is just as big this year. The response may not be.

A political scientist who studies the role of religion in politics, John Green, said evangelical Christians are disappointed by the Republican Congress’s failure to pass a constitutional amendment banning gay marriage or advance a federal ban on abortion.And, like other voters, they aren’t happy about the continuing violence in Iraq and the scandal over ex-Rep. Mark Foley’s sexually explicit messages to former congressional pages.

“The Republicans probably can’t win without good turnout from this group,” said Mr. Green, senior visiting fellow at the Pew Forum on Religion & Public Life in Washington and director of the Bliss Institute of Applied Politics at the University of Akron in Ohio.

Mr. Dobson, 70, and his Colorado Springs, Colo.-based organization are key figures in the Republican efforts to assure a big evangelical turnout on November 7.

“Rove certainly sees Dobson as the most important and politically influential evangelical leader,” the author of “The Elephant in the Room: Evangelicals and the Battle to Control the Republican Party,” Ryan Sager, said. “Dobson is someone who the White House works with extremely closely and constantly.”

His difficulties mirror the party’s. The Nashville rally was almost canceled after organizers failed to sell the 6,000 tickets they needed to fill the city’s Municipal Auditorium, forcing them to hold the event in the Two Rivers Church. Similar events in recent weeks in Minneapolis-St. Paul and Pittsburgh also drew smaller-than-anticipated crowds.

“Republicans take advantage of conservative Christian voters,” Lewis Lampley, 60, who attended the rally in Nashville, said. “They take our votes for granted.”

A new book by the deputy director of the Office of Faith-Based and Community Initiatives in the White House between 2002 and 2003, David Kuo, may add to the discontent. The book, “Tempting Faith,” alleges the White House exploited the faith- based effort for political purposes and that evangelical leaders including Mr. Dobson were dubbed “the nuts” by officials in Mr. Rove’s office.

They “were dismissed behind their backs and described as ‘ridiculous,’ ‘out of control,’ and just plain ‘goofy,”‘ Mr. Kuo wrote.

At a rally in St. Paul this month, Mr. Dobson acknowledged his flock’s discontent.”I’m going to speak to you honestly. I am and have been very irritated with the Republican Party,” he said.

Still, he’s doing his best to motivate his followers. When it comes to the top issue facing Christian voters today, winning the war against “Islamic fundamentalists,” Mr. Bush and his party “get it,” Mr. Dobson said.

His group is also putting its weight behind Republican candidates, such as Senator Santorum of Pennsylvania, who support its positions on social issues. Mr. Dobson is supporting a statewide ballot initiative to ban gay marriage in Tennessee, where the Republican mayor of Chattanooga, Bob Corker, is locked in a tight race with a Democratic congressman, Harold Ford Jr., for an open Senate seat.

The senior pastor at Two Rivers Baptist Church in Nashville, Jerry Sutton, said he believed Mr. Dobson’s effort would pay off. “There is a concerted effort to say conservative voters are going to stay home this year because they are disgusted with Mark Foley,”Mr. Sutton, 54, said. “It’s not going to work. Our congregation, we did voter registrations twice.They are very, very motivated to vote.”

A Nashville city council member who attended Mr. Dobson’s rally, Eric Crafton, 39, said the Foley scandal “is going to inspire people to vote even more, to vote for candidates who are going to stand up for the right values.”

Mr. Dobson is reaching out to his constituents through his daily radio show, which is syndicated nationwide and reaches an estimated 3.5 million listeners each week. In addition to Pennsylvania, his group also is organizing turnout drives in Minnesota, Maryland, Michigan, Ohio, New Jersey, and Montana.

In Minnesota, Mr. Dobson is trying to engineer a win for Michele Bachmann, a candidate for the House seat being vacated by Republican Mark Kennedy, who is running for the Senate. Ms. Bachmann, a Republican who opposes abortion and supported a state constitutional ban on same-sex marriage while in the Minnesota Senate, said the scandals in Washington and Mr. Bush’s low approval rating mean she faces a tight race in the socially conservative northern suburbs of Minneapolis.

“Republicans are at a low ebb tide this year, so it’s not a given the Republicans would hold this seat,” Ms. Bachmann, 50, said in an interview.

Focus on the Family operatives plan to distribute 250,000 voter guides in Minnesota churches to reach social conservatives, said Tom Prichard, 47, president of the Minnesota Family Council, a local affiliate of Mr. Dobson’s group. “It’s really a volatile election situation,” Mr. Prichard said.