Once virtually immune to Europe's economic woes, the euro has become vulnerable to the growth performance in the single currency zone following a French and a likely Dutch "no" to the European Union constitution.
Currency investors are likely to demand economic proof that the EU and its monetary union are working in the face of political turmoil and fading reform drive which are likely to follow a rejection of the charter.
This week, markets had the first taste of this change in investors' views of the European economy, whose poor performance had not been an obstacle against the euro charging to record highs versus the dollar only half a year ago.
The euro fell two per cent in as many days today, due to France's rejection of the EU charter on Sunday and a likely similar vote in the Netherlands today.
Its losses accelerated following a report today, later denied, that top policymakers in Germany had discussed risks to the euro's survival.
"We have seen, to some extent, a massive swing in the market's focus," said Thomas Stolper, global market economist at Goldman Sachs in London.
"Investors have stopped focusing on structural problems in the US economy and are focusing on the political situation in Europe and its effect on the long-term economic outlook."
"The speed of the euro's move shows that," he said.
The euro traded at its weakest level in nearly eight months today at $1.2224, after shedding more than two cents from late Monday.
It had reversed its entire bull run that started in mid-October last year and ended with record highs against the euro at $1.3667 in December.