Final answer:
Supreme Court justices consider the political climate when deciding to retire, as their successors are appointed by the current administration, potentially affecting the Court's ideological balance. The process can be highly politicized, as seen in historical examples such as Roosevelt's court-packing attempt and the contentious nomination processes of Merrick Garland, Neil Gorsuch, and Brett Kavanaugh.
Step-by-step explanation:
The question 'Why did Justice Souter wait until 2009 to retire?' pertains to the decision-making process behind Supreme Court justices' retirement. While the specific reasons behind Justice David Souter's retirement timing are not provided in the reference material, generally, Supreme Court justices consider the political landscape and the potential to influence their successor's appointment when deciding on retirement.
The appointment process for a new justice can become highly politicized, as exemplified by instances like President Franklin D. Roosevelt's attempt to expand the Supreme Court for political gain, Senate Majority Leader Mitch McConnell's decision to block President Obama's nominee Merrick Garland and later rush through Justice Amy Coney Barrett's confirmation, and the intense partisanship seen during Brett Kavanaugh's nomination.
These examples showcase the strategies which can be involved in appointing new justices and the potential for political battles that can arise from a vacancy on the Court.