Pro-Israel groups, afraid of losing one of their staunchest supporters in Congress, are pouring money into beleaguered Sen. Joe Lieberman's campaign as he tries to fend off a tougher-than-expected primary challenge. The three-term lawmaker is struggling to dispatch millionaire businessman Ned Lamont in the Aug. 8 primary. Lamont's fierce criticism of Lieberman's backing of the Iraq war and perceived closeness to President Bush has won him followers among hard-core Democrats. The primary is Aug. 8 and Lieberman has said he will run as an independent if he loses. Pro-Israel political action committees have donated to the Connecticut senator's campaign and have urged their national membership to give generously now and later, if Lieberman is forced to run as an unaffiliated candidate.