This paper analyzes how PAC contributions from defense contractors inf
luence members' votes for prodefense positions on the floor of the Hou
se of Representatives. Previous studies of defense voting in Congress
have emphasized the powerful effects of ideological predispositions on
members' roll-call votes on national defense. By contrast, PAC contri
butions are hypothesized to have a marginal impact. Even at the margin
s, the influence of PAC money is not likely to be the same for all mem
bers; it is hypothesized to be greater for moderate members than for l
iberal or conservative members. Because of the problem of simultaneous
influences of PAC money and roll-call votes, a two-stage least square
s estimation procedure is employed. The results once again confirm the
powerful effects of ideology on defense voting but also indicate that
PAC contributions exert a statistically significant (though marginal)
impact even when ideological predisposition is controlled. In additio
n, the results support the argument that those members with weaker ide
ological predispositions are more responsive to the effects of PAC mon
ey. Finally, the results indicate that, even at the margins, PAC contr
ibutions from defense contractors can influence the outcome of legisla
tive deliberations, especially when the vote margin is not very large.