Measurements of the Hubble Constant with a Two Rung Distance Ladder: Two
  Out of Three Ain't Bad
  The three rung distance ladder, which calibrates Type Ia supernovae through
stellar distances linked to geometric measurements, provides the highest
precision direct measurement of the Hubble constant. In light of the Hubble
tension, it is important to test the individual components of the distance
ladder. For this purpose, we report a measurement of the Hubble constant from
35 extragalactic Cepheid hosts measured by the SH0ES team, using their
distances and redshifts at cz < 3300 km /s , instead of any, more distant Type
Ia supernovae, to measure the Hubble flow. The Cepheid distances are calibrated
geometrically in the Milky Way, NGC 4258, and the Large Magellanic Cloud.
Peculiar velocities are a significant source of systematic uncertainty at z
$\sim$ 0.01, and we present a formalism for both mitigating and quantifying
their effects, making use of external reconstructions of the density and
velocity fields in the nearby universe. We identify a significant source of
uncertainty originating from different assumptions about the selection criteria
of this sample, whether distance or redshift limited, as it was assembled over
three decades. Modeling these assumptions yields central values ranging from H0
= 71.8 to 77.0 km/s/Mpc. Combining the four best fitting selection models
yields H0 = 73.1 (+2.6/-2.3) km/s/Mpc as a fiducial result, at $2.6\sigma$
tension with Planck. While Type Ia supernovae are essential for a precise
measurement of H0, unknown systematics in these supernovae are unlikely to be
the source of the Hubble tension
