Congressional Democrats are euphoric. After a protracted, six-month legal battle, Sen.-designate Al Franken finally toppled Sen. Norm Coleman (R-MN). Franken’s election awards Democrats the Holy Grail of 60 seats in the U.S. Senate. Democrats have been the majority party in the Senate since early 2007. But 60 votes is the magical number required to truly control the Senate. 

Sixty votes curtails filibusters, the right of a single senator to clog the Senate plumbing. And neither party’s had a bottle of parliamentary Drano this powerful since the Democrats boasted a filibuster-proof Senate supermajority in the late 1970s.

With the exception of the Supreme Court (for now), Democrats hold all of the reins to power in Washington. President Obama occupies the White House. Democrats command a substantial majority in the House. And with Franken, they now preside over a 60-vote bloc in the Senate.

After Coleman conceded, it didn’t take long for Democrats to raise expectations.

“With 60 votes now in the Senate, there’s no excuse for Democrats not passing our energy (and climate) bill,” said a senior House Democratic aide. The aide referred to the massive climate change legislation Democrats lugged through the House last week against all odds. The package faces dim prospects in the Senate. And that’s to say nothing of drilling into the next legislative boulder in the quarry: health care reform.

Sixty votes should be a blessing for Democrats.

Except when it isn’t.

First, the Democrats don’t truly have 60 votes in the Senate. With the addition of Franken, they have 58 (and technically, Franken isn’t a Democrat either. Democrats in Minnesota are known as members of the “Democratic Farmer Labor Party”). That’s because Sens. Bernie Sanders (I-VT) and Joe Lieberman (I-CT) caucus with the Democrats, but don’t define themselves as Democrats. Senate Majority Leader Harry Reid (D-NV) can sometimes get an earful in stereo from Sanders and Lieberman.

Sanders, a socialist, is arguably the most-liberal member of the Senate. And he’s more than willing to buck the Democratic leadership when he doesn’t feel the liberal wing gets a fair shake. Lieberman on the other hand is a moderate who’s plenty willing to come at the Democratic leadership team when he believes it veers too far to the left.

But the Democrats aren’t even quite at 58 votes. Two of the most-revered members of the body suffer from poor health. Sen. Edward Kennedy (D-MA) has rarely visited the Senate for more than a year because of a struggle with brain cancer. Sen. Robert Byrd (D-WV) is visibly slowing down in the past few years. He recently suffered a staph infection and spent several weeks in the hospital before his release Tuesday. So, depending on the day, the Democratic “supermajority” could be as scant as 56.

And then there are the moderate to conservative lawmakers who populate the Senate Democratic Caucus: Sens. Blanche Lincoln (D-AR), Mark Pryor (D-AR), Ben Nelson (D-NE), Bill Nelson (D-FL), Jon Tester (D-MT) and Arlen Specter (D-PA). This crowd is known to oppose the leadership on critical issues and often requires special courting. Plus, the big Democratic majority actually works against Reid and Co. The more Democratic votes, the more opportunity these six have to bolt the party on key votes and freelance. Or serve as holdouts that Democratic leaders must woo.

There’s a reason why former Senate Majority Leader Trent Lott (R-MS) titled his book “Herding Cats.” 

In a worst case scenario, the independence of the moderates drains the Democratic supermajority all the way down to a very ordinary 50 votes. And we haven’t even mentioned Sen. Dianne Feinstein (D-CA) who sometimes goes it alone on given issues.

If Democrats bind together and maybe bring along moderate Sens. Olympia Snowe (R-ME) and Susan Collins (R-ME), they can be a force to be reckoned with. But Sen. John Cornyn (R-TX), the chairman of the panel charged with electing Republicans to the Senate, could hardly contain his glee in this statement about Franken’s victory.

“With their supermajority, the era of excuses and finger-pointing is now over,” Cornyn said. “With just 59 votes, Senate Democrats in recent months have passed trillion-dollar spending bills, driven up America’s debt, made every taxpayer a shareholder in the auto industry and now want to take over America’s health care system. It’s troubling to think about what they might now accomplish with 60 votes.”

Of course, Cornyn knows that the fulcrum to secure Republican seats in 2010 is the 60 votes. His staff at the National Republican Senatorial Committee will craft ads that portray the election of Republican senators as the dead man’s switch to President Obama’s policy initiatives.

The only problem for Cornyn is that the real foe to these legislative priorities could be Democrats, not Republicans, who prevent Harry Reid and Mr. Obama from cobbling together 60 votes.

Like an oasis in the desert, the 60-vote Democratic supermajority is a mirage. Democrats hold 60 votes in name only. And it is far from a guarantee that Franken’s election cements their legislative agenda.

- Chad Pergram covers Congress for FOX News. He’s won an Edward R. Murrow Award and the Joan Barone Award for his reporting on Capitol Hill.