In their 2020-02-05 column, “Minority report: German politics”, The Economist writes:
In the 1970s West Germany’s two main parties, one centre-left, one centre-right, together captured over 90% of the vote. Today they are among half a dozen competing for Germans’ support. Such fragmentation complicates the business of forming governments. Last October voters in the eastern state of Thuringia returned a particularly complex result, depriving the government led by Bodo Ramelow, regional head of the Left party, of a majority. His left-wing, three-party alliance won just 42 of 90 seats. But today Mr Ramelow hopes that the fractious new parliament will vote to re-conﬁrm him for a second term as the state’s minister-president anyway. Minority governments in Germany rarely last, so what Mr Ramelow hopes to do is unusual: co-operating with liberal or conservative parties where possible to survive the entire term. His ﬁrst test may be his biggest. The opposition has not ruled out working with him on a case-by-case basis, but they will oppose him today.
What does where refer to? How can we analyse the grammatical structure of that sentence, particularly the portion I have indicated in bold?