Europe's top economy decided a decade ago to go nuclear-free by around 2020 but Merkel last year postponed the switch-off until the mid-2030s despite strong public unease.
Japan's nuclear emergency then prompted her last week to announce a three-month moratorium on the postponement and the temporary shutdown of Germany's seven oldest reactors pending a safety review.
She also said she would speed up the transition to renewable energy and reiterated Wednesday that for Germany, nuclear is a "bridge technology" until renewables like solar and wind power produce more electricity.
But her announcements have gone down badly, with critics calling it a knee-jerk reaction and one survey showing nearly seven out of 10 voters thought they were "pure electioneering" ahead of Sunday's crucial election.
It is "very clear that the moratorium has hurt" Merkel's Christian Democrats (CDU), Manfred Güllner from pollsters Forsa said.
Baden-Württemberg is the most important of seven electoral tests in 2011, and nuclear could tip the balance in an already tight race, ending 58 years of unbroken CDU rule. Merkel was not even born when they first took office.
The southwestern state has an economy the same size as Belgium's, a strong pillar of Europe's powerhouse at the start of what business daily Handelsblatt calls "a golden decade" for German exporters.
Daimler, Porsche and auto parts giant Bosch are proud to call the 10.8-million-strong state home, as do a whole army of lesser-known champions like Recaro (car and aircraft seats), Würth (screws) and Voith (engineering).
Another is family-owned Kärcher, conquering the world - and making it cleaner - with high-pressure blasters from its base in the well-ordered town of Winnenden outside state capital Stuttgart.
"We have a tradition of good engineering in this state," chief executive Hartmut Jenner proudly said at the firm's headquarters.
"People are dedicated to hard work and hard work is a part of their life. We have never laid off anyone for business reasons."
"I've never known anything other than the CDU here," said Gregor Baumstark, 32, a taxi driver. "Economically we are doing great. Everything works, firms are making profits, hiring."
But losing power in the state, the latest setback in Merkel's second term after a hammering by the Social Democrats (SPD) in Hamburg in February and ceding North Rhine-Westphalia in May, is what polls suggest might happen.
Surveys had already suggested a tight race because of a row over a mammoth rail project that last year sparked the ugliest and angriest clashes in living memory in normally tranquil Baden-Württemberg.
But events in Japan meant this and other burning local issues like education have been overtaken by nuclear power, with 68 percent of people in a recent poll saying it would have an "important influence" on their vote.
The main winners are set to be the ecologist Greens, fresh from more than doubling their share of the vote to seven percent in last Sunday's state election in Saxony-Anhalt.
Polls suggest they are set to record a strong score not only in Baden-Württemberg but also in Rhineland-Palatinate state in the west, likely forcing the SPD in power there to form a coalition with them.
In Baden-Württemberg, the vote could hand Germany its first ever state premier from the Greens, in power nationally 1998 to 2005 in coalition with the SPD under Gerhard Schröder.