The Henderson Moving Average (HMA) has some significant limitations. Technically, it should only be used when the data points come in equally spaced periods of time, and it has no mechanism for dealing with missing data.
In what is not quite kosher analysis, I have applied a HMA to the houses that poll fairly regularly. Essential usually produces a weekly estimate. Morgan and Newspoll typically produce a fortnightly result. And ReachTEL yields a monthly estimate.
To obtain a rough six month moving average across these houses, I have applied a 25-term HMA to Essential, a 13-term HMA to Morgan and Newspoll, and a 7-term HMA to ReachTEL. The results follow. Only Morgan saw the post 2014 Budget as the more significant slump for the Coalition. The other three pollsters had the late January come early February 2015 slump as the more significant. All agree the Coalition has been improving since the early 2015 slump, but an election winning position in the polls will require further improvement.