Final answer:
The line-item veto can cause an imbalance by enabling the president to reject parts of a bill, thus altering legislation unilaterally and diminishing legislative branch power.
Step-by-step explanation:
The line-item veto is a power that enables an executive to reject individual provisions of a bill without vetoing the entire bill. This power may cause an imbalance between the legislative and executive branches of government because it gives the president the ability to unilaterally alter legislation, essentially granting them the capacity to reshape legislation more to their preferences without full legislative oversight or approval.
When a president wields the line-item veto, it can significantly diminish the power of the legislative branch, as their negotiated and passed legislation can be partially negated according to the president's discretion.