Like an oasis in the desert, the 60-vote Democratic supermajority is a mirage. 

Yes, former comedian Al Franken is now Minnesota's senator-elect -- thanks to the state Supreme Court's ruling Tuesday -- giving Democrats enough members in the Senate to hit a filibuster-proof majority. This is no laughing matter. 

But that's on a really, really good day. For all intents and purposes, Democrats don't truly have 60 votes in the Senate. 

With the addition of Franken, they technically have 58. Sens. Bernie Sanders, I-Vt., and Joe Lieberman, I-Conn., caucus with Democrats but don't define themselves that way. 

Sanders, a socialist, is arguably the most liberal member of the Senate, so he's more than willing to buck the Democratic leadership when he doesn't feel the liberal wing gets a fair shake. Lieberman, by contrast, is a moderate who's plenty willing to challenge the Democratic leadership when he believes it veers too far to the left. 

But the Democrats aren't even at 58 votes on most days. 

Two of the most revered members of the chamber suffer from poor health. Sen. Ted Kennedy, D-Mass., has rarely visited the Senate for more than a year because of a struggle with brain cancer. Sen. Robert Byrd, 91, of West Virginia who has been slowing down in the past few years, recently suffered a staph infection and spent several weeks in the hospital before his release Tuesday. 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-Ark.; Mark Pryor, D-Ark.; Ben Nelson D-Neb.; Bill Nelson, D-Fla.; Jon Tester, D-Mont.; and Arlen Specter, D-Pa. 

This crowd is known to oppose the Democratic leadership on critical issues and often requires special courting. With them, the big Democratic majority could work against Senate Majority Leader Harry Reid, D-Nev., since it gives these moderates the perceived opening to bolt the party on key votes and freelance -- or act as holdouts that Democratic leaders must woo. 

There's a reason why former Senate Majority Leader Trent Lott, R-Miss., titled his book "Herding Cats." 

In a worst-case scenario, the independence of the moderates whittles the Democratic supermajority all the way down to a very ordinary 50 votes -- or fewer. 

Sen. Dianne Feinstein D-Calif., sometimes goes it alone on given issues. 

And Franken isn't technically a Democrat either, since Democrats in Minnesota are known as members of the "Democratic Farmer Labor Party." 

Despite Franken's reputation as an unabashed liberal commentator before his Senate run, he insisted Tuesday he's not an automatic 60th vote. 

"I know there's been a lot of talk about the fact that when I'm sworn in I'll be the 60th member of the Democratic caucus, but that's not how I see it," he said. "The way I see it, I'm not going to Washington to be the 60th Democratic senator. I'm going to Washington to be the second senator from the state of Minnesota, and that's how I'm going to do this job." 

Despite the reality of Democrats' less-than-ideal hold on power in Washington, members of both parties still pointed to Franken's victory as the grease that would let the Democratic agenda slide through. 

Democrats raised expectations for themselves, hailing Franken's win as key for efforts to pass health care reform and major energy policies. 

"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, referring to the sweeping cap-and-trade legislation Democrats lugged through the House last week against all odds. The package faces dim prospects in the Senate. 

Sen. John Cornyn, R-Texas, chairman of the National Republican Senatorial Committee, interpreted the impact of Franken's win as nothing short of complete and total Democratic domination in Washington. He said that means Democrats essentially own every policy that comes out of the nation's capital.

"With their supermajority, the era of excuses and finger-pointing is now over," Cornyn said in a written statement. "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." 

His staff at the National Republican Senatorial Committee will no doubt use that pitch to their advantage in the 2010 mid-term elections. 

But the real foe to President Obama's legislative priorities could end up being Democrats, not Republicans, as they potentially prevent Reid and the president from cobbling together a clean 60 votes. 

Sen. Bob Menendez, D-N.J., who is Cornyn's counterpart in the Democratic Party, acknowledged the hurdles ahead on Tuesday. 

While he said Franken's victory gives Democrats a "tremendous opportunity to move a progressive agenda ahead," the 60-vote supermajority is not a sure thing on any given day. 

"We obviously have a few illnesses. That`s the first challenge towards it," he told MSNBC. "Secondly, our caucus is not monolithic." 

He said Franken would give Democrats "a little more strength" to pursue their agenda. 

FOX News' Chad Pergram contributed to this report.