Aipac, which refers to itself as "America's pro-Israel lobby," officially is not a political action committee---it does not make direct contributions to members of Congress and other elected officials. But it encourages its membership and supporters to do so.
The organization's non-partisanship diminished considerably in the 1990s and 2000s as it overtly allied itself with neo-conservatives, lobbying for war against Iraq, for the confirmation of ultra-conservative John Bolton as United Nations ambassador (during the Bush administration), and against the confirmation of Charles Freeman as the Obama administration's chairman of the National Intelligence Council.
The lobby's overtly right-wing shrillness, associated most closely with Israel's Likud Party platform, led to the creation of J Street, a left-leaning pro-Israel lobby "founded to promote meaningful American leadership to end the Arab-Israeli and Palestinian-Israel conflicts peacefully and diplomatically."