WASHINGTON - Al Franken's victory in the long-contested Minnesota U.S. Senate race means Democrats will control 60 Senate seats for the first time in 30 years, but they will still face obstacles to passing major legislation.

On paper, the party now has the muscle to block any Republican filibuster, since it takes 60 votes under Senate rules to end debate and move to a final vote.

However, two key Democratic senators are battling serious illnesses, two others are independents who caucus with the party but aren't sure votes with the majority, and all senators have diverse constituencies that sometimes lead them to break ranks with their parties.

As a result, it's unlikely the 58-year-old Harvard-educated former comedian and now senator-elect will make a dramatic difference this year as his party and the White House attempt to overhaul health care, limit carbon emissions and pass other major legislation - often in the teeth of Republican opposition.

"It's a numerical achievement, but not necessarily a political one," said Ross Baker, a political science professor at Rutgers University.

Franken said he'd join the health committee, which is writing health care legislation, and the judiciary committee, which is to begin hearings on the nomination of federal appellate Judge Sonia Sotomayor to the U.S. Supreme Court on July 13.

One obstacle faced by Democrats in getting all 60 of their votes is that Sens. Robert Byrd of West Virginia and Edward Kennedy of Massachusetts are ailing and frequently have been absent.

Also, Vermont's Bernard Sanders and Connecticut's Joseph Lieberman are independents who are counted as part of the Democratic caucus, but Sanders is considered more liberal than most Democrats and Lieberman is more allied with Republicans on national security issues.

Amassing 60 votes also will depend on the issue at hand. When climate change legislation came up in the House of Representatives last week, 44 Democrats voted no on the party plan and Republican votes were needed to pass it.

In the Senate, that bill's "going to need 60 votes to stop a filibuster, and you can easily name 10 or 15 Democrats who aren't going to vote for a bill at all," said Steven Schier, a political science professor at Carleton College in Northfield, Minn.

It's also not certain that 60 Democratic-controlled votes would back a health care plan, though under Senate rules adopted this year the plan would need only 51 votes if it's considered after Oct. 15.

Still, Republicans said 60 votes under Democratic control will make a difference.

"With just 59 votes, Senate Democrats in recent months have passed trillion-dollar spending bills, driven up America's debt, made every American taxpayer a shareholder in the auto industry and now want Washington to take over America's health care system. It's troubling to think about what they might now accomplish with 60 votes," said National Republican Senatorial Committee Chairman John Cornyn of Texas.

Where Franken could make a difference in the Senate is on procedural votes, the little-noticed votes on parliamentary maneuvers that keep legislation moving.

"The real impact of 60 is that it will help our ability to get to the underlying issues more quickly," said Sen. Thomas Carper (D., Del.).