Churchill Downs stock rallied Monday, rising $3.22 on heavy trading. What drove the increase can only be speculated, but it came the day before Indiana legislators are to vote on a bill that expands gambling at racetracks and riverboats, and video lottery legislation is to be introduced in Kentucky.The Indiana gambling bill, which the House must take action on by midnight tonight, would allow electronic pull-tab machines at the state's two racetracks. Chruchill Downs Inc. is the majority owner of Hoosier Park in Anderson, Ind. The pull-tab machines are to compensate for the elimination of a $26 million subsidy the Indiana Horse Racing Commission receives from riverboat gambling. The subsidy is to be phased out over three years.Also, legislation that would allow Kentucky racetracks to offer video lottery wagering is expected to be unveiled Tuesday. The racing industry has scheduled a news conference for 1 p.m. at the Capital Annex in Frankfort.The Louisville-based racing conglomerate watched its stock rise $3.22 Monday, an increase of nearly 9%. Trading was heavy with 75,500 shares changing hands compared with the 100-day average volume of 24,000.Churchill's stock may have been helped by a flurry of activity throughout the stock market. The Dow Jones Industrial Average climbed by more than 100 points for a second consecutive trading day. The Dow jumped 178 points to close at 10,146, an increase of 1.8%. A similar rally on Friday drove the Dow up 134 points. The Nasdaq on Monday moved up 45 to 1,770.