Votto is the hottest hitter in the majors since the All-Star break, batting .561. He also walked, singled and doubled, giving him an NL-leading 37 multihit games.
Leake (9-5) allowed four hits in eight innings to win his fourth straight start. He allowed just two earned runs in his last 30 innings for a 0.60 ERA.
Jaime Garcia (3-4), activated from the 15-day disabled list earlier in the day, made his first start since June 2 and gave up three runs and four hits in six innings. He is 10-3 against the Reds, including 7-1 at home.
Garcia held the Reds to one hit before the sixth, when Leake reached on a leadoff single, Brandon Phillips walked with one out and Votto hit his 19th homer, a drive to straightaway center estimated at 418 feet.
Votto's one-out single in the fourth ended a string of 8 1/3 hitless innings for Garcia counting a rehab start with Triple-A Memphis. Stephen Piscotty singled for St. Louis' first hit with two outs in the fifth.
Cardinals cleanup man Jhonny Peralta is 2 for 20 against Leake after going 0 for 3 against the right-hander.
FEW AND FAR BETWEEN
A win Wednesday would give the Reds just their fourth series win out of 35 played since the 2003 season against the Cardinals. They've dropped nine straight series in St. Louis.
Cardinals: OF Randal Grichuk (groin) sat a second straight day but could be in the lineup Wednesday. RHP Jordan Walden (bicep) was set to begin a rehab with Triple-A Memphis. C Yadier Molina went the distance a day after being replaced in the fifth due to illness.
Rookie Anthony DeSclafani allowed three runs in seven innings and got no decision in a loss at Colorado his last time out. The Reds will recall lefty Mike Holmberg from Triple-A Indianapolis as the replacement starter for Johnny Cueto against the Pirates. St. Louis' John Lackey is 5-1 with a 1.75 ERA his last eight starts.