CDU till 2002. Then as a "retire Kohl" vote FDP, CDU under Merkel. Btw how does it look for her re-election? Also, in Germany do people vote more based on their constituency's candidates or just their preferred parties? Also, why is it that Merkel has approvals in the 60's but CDU would only get 30's or 40's in terms of votes according to recent-ish polls?
I'm no expert on Germany, but with regards to her re-election right now it looks like the only possible result of the next election is a CDU-SPD "grand coalition", with whichever party comes in first getting the Chancellorship. The CDU is still in first place by a good margin, so the odds are very strong that Merkel will be Chancellor under a CDU-SPD coalition, just like she was from 2005-2009.
Why did the original grand coalition fall apart anyway?
Also would it be possible to have a merger of the Pirate Party and the FDP? What would be the results of such a merger?
I'm not really familiar with why the grand coalition failed, sorry.
With regard to the Pirates and the FDP, I think a merger of the two is very unlikely. The Pirates seem fairly left-leaning, supporting things like a universal basic income, although their positions on anything other than their signature issues are not well defined. Their support is kind of hard to pin down (a lot of it seems to be just anti-"establishment" without any particular ideology), but it seems like their biggest group of supporters are former Greens. I don't think many of their supporters would like a merger with the FDP.
The other parties seem to be taking a cordon sanitaire
stance towards the Pirates right now and hoping that they'll just fade out over time. It seems like the CDU and SPD both would rather form a grand coalition than work with the Pirates, and given the amount of support both parties have a coalition between the two will essentially always be mathematically possible. The Pirates also don't seem to have a great desire to work with any of the other parties, as playing the outsider works for them right now. They'd probably lose a lot of support if they ever entered government with anyone.