The comedian Al Franken will be welcomed by fellow Democrats at a lunch on Capitol Hill today after he has been sworn in as senator, taking the party’s Senate vote bank to the magic threshold of 60.

His arrival makes the Democrats the first party in three decades to attain the fabled super majority, allowing them – in theory – to override Republican filibusters and implement their legislative agenda.

A week after Mr Franken was declared Senator of Minnesota, however, doubts are growing as to how politically useful a super majority will be when the hard bargaining over controversial issues such as healthcare and climate change begins.

The Democrats' majority exists more on paper than in reality. Two of its most reliable progressive Senators, Ted Kennedy and Robert Byrd, suffer such persistent age-related ill health that they cannot be relied on to attend key votes.

Another of the 60 votes belongs to the independent Joe Lieberman who, while loyal to a broadly Democratic agenda, will not commit to voting along party lines. A handful of other Democratic senators, including the Republican defector, Arlen Specter, remain on the right of the party and ideologically opposed to some of Barack Obama’s more progressive agenda.

All this has left Harry Reid, the Senate majority leader, feeling nervous about the expectations foisted on him by the attainment of the super 60.

Senate majority and minority leaders are not like the chief whips at Westminster. In the US House, business is done by consensus at party level and on the floor, with thousands of hours of horse-trading going into shaping a bill. The Democratic Party also houses a wide spectrum of opinion, and several senators in swing seats are vulnerable to Republican accusations that they are supporting a far-left liberal agenda.

“We have 60 votes on paper,” Mr Reid noted the morning after Mr Franken’s victory was declared. “But we cannot bulldoze anybody, it doesn’t work that way. My caucus doesn’t allow it. And we have a very diverse group of senators philosophically. I am not this morning suddenly flexing my muscles.”

Sixty votes or not, Mr Reid’s job looks as much like herding cats as it did before. What he fears is the added pressure from voters hungry for change who no longer see excuses for failing to move ahead with the Obama agenda.

So concerned are party leaders about raised expectations that word has gone out around the party to dampen down the celebrations. Mr Franken, who arrived in Washington yesterday, spoke soberly of being the “second senator from Minnesota” rather than the 60th Democratic vote.

One suggested compromise is for Democrats to band together to overcome Republican filibusters even if they oppose the legislation on a later vote.

The filibuster is a technique of endless debate on the Senate floor until the time allotted to the legislation in question has lapsed, leaving no opportunity for a vote.

With 60 votes, a party can shut down the debate – a cloture vote – and move straight to voting on the Bill, requiring only a simple majority to pass.

Party leaders reason this will allow individual senators to defend themselves to constituents on the ground they did not vote for the Bill itself. Will it work? Obama can only hope so, as he heads to the Hill with contentious legislation on the hot-button issues of healthcare, climate change and immigration. Let the games begin.

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