President Clinton had the Line Item Veto. He used it very effectively. In fact, he is one of the few Presidents that ever had a surplus and not a deficit.
It was Former NY Mayor Rudy Giuliani (Republican) that went to the Supreme Court. The Conservative Supreme Court members voted that the Line Item Veto was unconstitutional since it gave too much power to the President.
Today, "We the People" have no idea what our Political Leaders are voting on because legislation has many unrelated line items. These Line Items are added to get votes from other Political Leaders and to provide kickbacks to those that funded a Political Leaders campaigns for office. In other words, these are BRIBES to get legislation passed or payback the wealthy.
It is the Line Items themselves that should be "Unconstitutional", since "We the People" do not get a clear understanding of what our Political Leaders are voting on. In most cases, the Political Leaders themselves don't know what they are voting on...only that they got their perk (bribe). For Example: Are our Political Leaders voting for legislation to fund the Government or are they voting to change financial regulations so the people are responsible for bailing out financial firms if their business strategy fails?