Barack Obama may not have been on the ballot. But the Republican victory in Wisconsin's gubernatorial recall election on Tuesday was a near unmitigated disaster both for him and his party, one that will reinforce the emerging doubts over his prospects of re-election in November.

Democrats were advancing predictable excuses yesterday. Mr Obama didn't get involved in the campaign, they point out, while incumbent Scott Walker vastly outspent his Democratic challenger Tom Barrett.

Anyway, they could console themselves, exit polls suggested the President is still ahead of Mitt Romney in the state. Probably, too, it was a tactical mistake to try to get rid of a first-term governor before he had served 18 months in office and who had not been accused of corruption. There have been only three attempts to recall governors since 1921, and Mr Walker was the first to survive.

But the mitigating circumstances end there. Mr Walker's sin had been to take on the public sector unions, trimming benefits and limiting collective bargaining rights, to help reduce Wisconsin's budget deficit. The recall was meant to be a show of strength for organised labour. The outcome was exactly the opposite.

Instead, the unions – a vital source of Democrat votes and funding – have been badly weakened, while the result proves that the Tea Party-driven ideas about fiscal austerity and deficit-cutting that propelled Republicans to their 2010 midterms triumph, are – contrary to some reports – very much alive. By their ferocious opposition to the young and telegenic Mr Walker, Democrats have merely created another conservative star.

And it couldn't have happened in a worse place. Wisconsin, like Michigan, Ohio and Pennsylvania, will be an important rust-belt battleground in November. Historically, the state has leant Democratic.

The last Republican to carry it was Ronald Reagan in 1984, and Mr Obama won by 14 points in 2008. But the Democratic victories in both 2000 and 2004 were razor thin, and national polls show Mr Obama losing ground among middle and lower-income white voters, a big chunk of the Wisconsin electorate.

And Mr Romney, who now inherits the impressive Walker operation, is not the only one from his party hoping for a win in the state on November 6.

That day, Wisconsin voters will also fill the senate seat made vacant by the retirement of Democrat Herb Kohl. The recall result suggests Republicans have a real shot at winning, and maybe regaining control of the US Senate in the process.

One way and another, Tuesday was a bad day for Democrats.