Republicans didn’t try to defund the organization when they held both houses of Congress and the presidency. It was not an issue that unified Republicans at the time. Now it is. If in the next few years Republicans again hold both houses of Congress and the presidency, the organization is likely to be defunded. It would not be possible to say that if pro-lifers had not taken on this fight. Nor does it seem likely that we would have won the Dornan amendment (cutting off funding for abortion in D.C.) without having the Planned Parenthood fight.
The public has long associated Planned Parenthood primarily with contraception, not abortion, and this fight was also useful in starting to change that. If pro-lifers make progress on this front — for example, by working harder to challenge the ridiculous spin put out by the organization that abortion accounts for only “3 percent” of its activities — this will be a winnable issue. It won’t be an issue that pro-lifers can win only by threatening to bring the budget down.
Update: For more on the ridiculous spin of the organization’s defenders, see here.