Truman and his staff knew it was highly likely that any civil rights plank would lead to Southern delegates staging a walk-out in protest, but Truman believed that civil rights was an important moral cause and ultimately abandoned his advisers' attempts to "soften the approach" with the moderate plank; so the President supported and defended the "Crackpot" Biemiller plank, which passed by 651.5 votes to 582.5. It also received strong support from many of the big-city party bosses, most of whom felt that the civil rights platform would encourage the growing black population in their cities to vote for the Democrats. The passage of the civil rights platform caused some three dozen Southern delegates, led by South Carolina Governor Strom Thurmond, to walk out of the convention. The Southern delegates who remained nominated Senator Richard Russell Jr. from Georgia for the Democratic nomination as a rebuke to Truman. Nonetheless, 947 Democratic delegates voted for Truman as the Democratic nominee, while Russell received only 266 votes, all from the South. Truman's first choice for his running mate was Supreme Court Justice William O. Douglas, hoping that it might make the ticket more appealing to liberals. Douglas refused the nomination. Needing an alternative, Truman then selected Senator Alben W. Barkley from Kentucky, who had delivered the convention's keynote address, as his running mate, with this nomination being made by acclamation.