Future US economic policy depends on the make-up of the US Senate. If Barack Obama wins the presidency on 4 November and the Democrats get a filibuster-proof majority of 60 seats, they can pass their legislative wish list unchecked, including business-unfriendly items. With 12 Republican seats of the current 49 seriously contested, it will be close.

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A number of Bills backed by Democratic lobbying groups and congressional Democrats have been blocked by the threat of Republican filibusters.

Removing the threat of a Republican filibuster possibility diminishes the need to craft bipartisan legislation. It thus increases the likelihood that business-unfriendly legislation in labour relations, environmental constraints, taxation and international trade could make it to the new president’s desk.

If senators voted along party lines, the Democrats would need 60 seats to overcome Republican filibusters. However, they don’t. Independent senator Joe Lieberman is increasingly detached from the Democratic caucus and Democrat Jim Webb is highly independent, so even with 38 senators, the Republicans might sustain some filibusters. Conversely, some Republicans are unreliable; 10 likely members of the new senate either voted for comprehensive immigration legislation or were part of the 2005 so-called Gang of 14 bipartisan deal on judge confirmations.

Of the 23 current Republican seats, 12 are seriously contested. Democrat pickups seem probable in Virginia, New Mexico, Colorado and Alaska. Three further incumbent senators, Elizabeth Dole, John Sununu and Gordon Smith trail in polls and appear vulnerable. With those losses and no gains, the Republicans would be down to 42, vulnerable to waverers. Five further seats lean Republican, but are vulnerable. Thus a Democrat pickup of 9-10 seats seems entirely possible. US business leaders may face a restless couple nights of sleep.