  We analyze radio tracking data obtained during 1311 orbits of the MESSENGER
spacecraft in the period March 2011 to April 2014. A least-squares minimization
of the residuals between observed and computed values of two-way range and
Doppler allows us to solve for a model describing Mercury's gravity, tidal
response, and spin state. We use a spherical harmonic representation of the
gravity field to degree and order 40 and report error bars corresponding to 10
times the formal uncertainties of the fit. Our estimate of the product of
Mercury's mass and the gravitational constant, $GM = (22031.87404 \pm 9 \times
10^{-4})$ km$^{3}$s$^{-2}$, is in excellent agreement with published results.
Our solution for the geophysically important second-degree coefficients
($\bar{C}_{2,0} = -2.25100 \times 10^{-5} \pm 1.3 \times 10^{-9}$,
$\bar{C}_{2,2} = 1.24973 \times 10^{-5} \pm 1.2 \times 10^{-9}$) confirms
previous estimates to better than 0.4\% and, therefore, inferences about
Mercury's moment of inertia and interior structure. Our estimate of the tidal
Love number $k_2 = 0.464 \pm 0.023$ indicates that Mercury's mantle may be
hotter and weaker than previously thought. Our spin state solution suggests
that gravity-based estimates of Mercury's spin axis orientation are marginally
consistent with previous measurements of the orientation of the crust.
