The gloomy electoral outlook for Republicans is growing even darker in the wake of a scandal over sexually explicit messages sent by a congressman to a teenage boy who had served as a congressional page, according to political analysts.

“I think the environment is as bad as it has ever been for Republicans,” an analyst of Senate races for the Washington-based Cook Political Report, Jennifer Duffy, said. “The best thing for Republicans right now is the fact that they’re not here. I think every member would be cornered in some part of the Capitol.”

“If Republicans lose Congress badly, we’ll look back at this as the tipping point,” another prominent analyst, Chuck Todd, said. “It certainly feels like this is big.”

Democrats need to pick up six seats to win control of the Senate and 15 seats to take charge in the House. A year ago, many analysts dismissed both prospects as unlikely or even impossible. However, the protracted violence in Iraq and a steady stream of corruption cases involving members of Congress and lobbyists such as Jack Abramoff have eroded voter confidence in the Republican leadership, according to polling data.

Now, the same congressional leaders are struggling to explain why they did little to explore early indications that a Florida congressman, Mark Foley, had taken an inappropriate interest in young staffers.

Conservative political activists said the scandal was unlikely to move many voters into the Democratic column but could lead some on the right to stay home.

“I think this is a real problem for the Republicans as they, right or wrong, are seen as the guardians of values,” the president of the Family Research Council, Tony Perkins, told CNN. “This is going to be, I think, very harmful for Republican turnout across the country.”

A leader of evangelical Christians, James Dobson of Focus on the Family, condemned Mr. Foley but seemed less sure of the incident’s political impact.

“Who can overlook what Foley has done? I mean, that is breathtaking,” Mr. Dobson said yesterday on a radio show hosted by a conservative commentator, Laura Ingraham. He called the episode “terrible” and compared it to President Clinton’s relationship with a 22-year-old White House intern, Monica Lewinsky.

Mr. Dobson said voters might forget about the Foley affair by Election Day, but conservatives are still “ticked” that the GOP has failed to push measures of interest to so-called values voters.

“The Republicans have done very little that they care about,” Mr. Dobson said. However, he said Democrats would be even worse. “I just can’t sit this one out,” the evangelical leader said. “I don’t think we can afford to teach the Republicans a lesson that I wish they would learn on their own.”

Mr. Todd, who edits a political newsletter known as the Hotline, said even a slight dip in turnout among conservatives could tip the balance to the Democrats. “Waves happen because one party’s voters are depressed,” he said. “A few points is all the Democrats need to turn a 12-seat gain into 35.”

Another analyst, Larry Sabato of the University of Virginia, noted that the wrongdoing by Mr. Foley, who resigned on Friday, is easy to comprehend and shocking even to voters who yawn at reports of illegal influence-peddling in Washington.

“This connects,”Mr. Sabato said. “This is beyond the pale and every parent identifies with this.” Mr. Sabato said control of the House is a toss-up at this point, with the Democrats still facing an uphill battle to win the Senate. “The Senate is probably just out of reach,” he said. “They need some luck. It isn’t impossible.You can see how it could happen.”

According to recent polls, Democrats are favored to pick up Senate seats in Pennsylvania and Montana. In Missouri, Ohio, Rhode Island, Tennessee, and Virginia, Democrats stand a decent chance of picking up Republican Senate seats, though the races are closer.

Only in a couple of states, such as New Jersey and Maryland, do Republicans seem to have a real possibility of taking Democratic seats and staving off a loss of control.

A congressional scholar at the Brookings Institution, Thomas Mann, said yesterday that he considers a Democratic takeover in the House “a near certainty” and in the Senate “a 50/50 proposition.” Mr. Mann said the Foley scandal was a factor, but that Republicans were already staggering from a leak of a pessimistic intelligence report about Iraq and news of a new book in which a veteran journalist, Bob Woodward, describes President Bush and the White House as “in denial” about the state of the war.

The Foley affair could also pose a particular challenge for one congressman, Thomas Reynolds, who represents a district upstate between Buffalo and Rochester. Mr. Reynolds, who runs the fund-raising committee for House Republicans, was told in the spring that Mr. Foley may have acted inappropriately toward pages. He said he alerted the Republican speaker of the House, Dennis Hastert, to the issue, but Mr. Hastert said he had no recollection of the contact.