On the Paradoxical Impact of Blending by Red Clump Giants
  The impact of blending by RCGs (red clump giants, or relatively metal-rich
red horizontal branch stars) is discussed as it relates to RRab and classical
Cepheids, and invariably establishing an improved distance scale. An analysis
of OGLE Magellanic Cloud variables reaffirms that blending with RCGs may
advantageously thrust remote extragalactic stars into the range of
detectability. Specifically, simulations of Magellanic Cloud RRab and RCG
blends partly reproduce bright non-canonical trends readily observed in
amplitude-magnitude space ($I_c$ vs.~$A_{I_c}$). Conversely, the larger
magnitude offset between classical Cepheids and RCGs causes the latter's
influence to be challenging to address. The relative invariance of a Wesenheit
function's slope to metallicity (e.g., $W_{VI_c}$) implies that a deviation
from the trend could reveal blending and photometric inaccuracies (e.g.,
standardization), as blending by RCGs (a proxy of an evolved red stellar
demographic) can flatten period-Wesenehit relations owing to the increased
impact on less-luminous shorter-period Cepheids. That could partly explain both
a shallower inferred Wesenheit function and over-estimated $H_0$ values. A
consensus framework to identify and exploit blending is desirable, as presently
$H_0$ estimates from diverse teams are unwittingly leveraged without
homogenizing the disparate approaches (e.g., no blending correction to a
sizable $\simeq 0.^{\rm m}3$).
