RK: Thanks for the reminder of the difference, which I take to mean that, for the whole election combined (district and PR) the party counts more than the individual candidate (correct me if I've misinterpreted you). I would note that polls overall, for both LH and UH, show voters paying more attention to the party and less to individual candidates than in the past. Even incumbents who had won their district seats by double-digits lost them in 2009 (and I believe in 2005 as well).

ESK: Yes-in the local districts, party and party leader image will count more in HOR's SSD than in HOC's large SNTV district where the personal vote will matter more; and in the PR districts, party and party leader image will count for more in the HOR's closed list than in the HOC's open list districts. This should follow from Carey and Shugart's famous model:
Seat allocation formulas affect candidates' incentives to campaign on a personal rather than party reputation. Variables that enhance personal voteseeking
include: (1) lack of party leadership control over access to and rank on ballots, (2) degree to which candidates are elected on individual votes independent of co-partisans, and (3) whether voters cast a single intra-party vote instead of multiple votes or a party-level vote.
District magnitude has
the unusual feature that, as it increases, the value of a personal reputation rises if the electoral formula itseff fosters personal vote-seeking, but falls if the electoral formula fosters party reputation-seeking.
("Incentives to Cultivate a Personal Vote:
a Rank Ordering of Electoral Formulas," Electoral Studies Vol. 14, No. 4).

But then there is also the malapportionment issue. The HOC districts are more malapportioned in favor of rural areas that it affects and distorts the vote, especially in the single seat districts. As Mike Thies has pointed out, this was one of the major reasons the LDP won more seats in the 2010 HOC election than the DPJ, even though the DPJ won more votes in both kinds of districts. In some cases in the 2010 HOC election a 4% vote swing in single seat local districts could produce
40+% difference in seat wins compared to the 2007 HOC
election!

So all this means that trying to predict outcomes in the HOC where the results in many ways are artificially determined by the nature of the electoral system is especially difficult. You may well be right that both DPJ and LDP will lose seats in the next HOR election; but whether that will also occur in the next HOC election...

Best,
Ellis Krauss