The Republican takeover of the Senate, a result of crucial victories by candidates opposed to abortion, has set off cautious celebration among anti-abortion activists and alarm bells in the opposing camp. ``The threat to choice is greater today than it has been in decades,'' said Kate Michelman, president of the National Abortion and Reproductive Rights Action League. NARAL and its allies spent millions of dollars in the closing weeks of the campaign supporting Democrats for Senate who favor abortion rights against Republicans who oppose them. But in the five most closely contested of these races -- Colorado, Georgia, Minnesota, Missouri...