The difficulty Congressional Democrats face on hot-button social issues was on full display Wednesday as the Senate narrowly turned back a gun-rights amendment to the Defense authorization bill.

The party’s more liberal Members hustled to defeat an amendment by Sen. John Thune (R-S.D.) that would have allowed gun owners with concealed-carry permits to bring firearms into other states with similar regulations.

But Majority Leader Harry Reid (D-Nev.) and 19 of the Democrats’ more moderate Members — half of whom were elected in 2006 and 2008 — voted in favor of Thune’s amendment.

The measure fell short of the 60 needed for passage on a 58-39 vote.

“We are a big-tent party, and we recognize that there are colleagues across the country who represent the interests and the views of their state,— Democratic Senatorial Campaign Committee Chairman Bob Menendez (N.J.) said. “And so this is never going to be a monolithic vote on any single issue, largely speaking.—

Sen. Frank Lautenberg (D-N.J.), who led the charge against the gun amendment, echoed that sentiment, saying: “We do have to respect the other person’s decision. I would have preferred we had 100 percent of our Conference, but we had enough to win.—

For Democratic moderates, “you’ve got to come down and take positions on issues even when you don’t want to,— said Sen. Claire McCaskill (D-Mo.), who sided with Lautenberg in opposing the amendment.

“This is part of what we signed up for,— McCaskill added. “You can’t make everyone happy on anything.—

“I think that’s called being a moderate. Both ends are mad,— she quipped.

The gun issue has proved vexing to Democrats all year. An amendment by Sen. John Ensign (R-Nev.) allowing guns on federal lands was successfully added to legislation granting the District of Columbia a voting Member of the House, effectively killing that bill for the year.

Sen. Tom Coburn (R-Okla.) successfully added an amendment to the credit card bill allowing guns onto federal land. Both measures easily passed the Senate.

Democratic moderates have wielded a heavy hand in policy debates this year — playing an integral part in crafting the $787 billion stimulus package, for example. In the Senate they have formed the Moderate Dems Working Group to coordinate their efforts.

But Senate Democratic aides maintain that when it comes to floor votes, controversial social issues like gun control are more likely to reveal fissures than are health care and climate change bills.

“Gun issues are a different animal. There’s an expectation that votes like this will bring out the differences within our Caucus,— a Senate Democratic aide said. “I don’t think that extends to other issues where there’s a strong sense of unity.—

But in the House, the issue of abortion has Speaker Nancy Pelosi (D-Calif.) scrambling to keep her party from derailing health care legislation.

Nineteen Democrats last month sent a letter to Pelosi threatening to oppose the health care bill — which needs every Democratic vote it can get — if it doesn’t clarify that federal dollars won’t be used for abortions.

Abortion foes say the House health care bill opens the possibility that the Health Benefits Advisory Committee will recommend that abortion services be included as part of a benefits package. Unless the bill has a clear exclusion, they say, abortion services could end up being part of a government-subsidized health care plan.

Pelosi on Wednesday tried to reach a compromise on the issue in a private meeting with three key Democrats: Rep. Diana DeGette (Colo.), Pelosi’s point person on the Energy and Commerce Committee, and anti-abortion Reps. Mike Doyle (Pa.) and Tim Ryan (Ohio).

Democrats who oppose abortion say Pelosi has yet to respond to their concerns over the health care bill — and some are threatening the worst if those concerns go unanswered.

“They can continue to ignore us if they want, but at their peril,— warned Rep. Bart Stupak (D-Mich.), co-chairman of the Pro-Life Caucus. He predicted that anti-abortion Democrats would make their voices heard “if we have to come and force the issue on the floor— when the rule for debating the health bill comes to the floor.