I recently wrote in two custom political parties, and began a game using one of them on a custom race. Everything runs fine until I try to declare war, when clicking the VOTE button causes the game to crash.

Debugg.err provides the following, which seems pretty normal:
Debug Message: Popup Manager Update: Updating window with ID=10
Debug Message: Popup Manager Update: Unhiding MessageBoxWnd
Debug Message: Popup Manager Update: Updating window with ID=29
Debug Message: Popup Manager Update: Unhiding ElectionWnd

Here's the relevant portions of the text of the PoliticalParties.xml file, minus the description section and using [] rather than <> so the code can be displayed:

[PoliticalParty InternalName="Red Brood"]
[ID]8[/ID]
[DisplayName]Red Brood[/DisplayName]
[Model]gfx/Government/RedBrood.png[/Model]
[OpposingParty]Grey Brood[/OpposingParty]
[Bonus]7:30 15:20[/Bonus]
[Penalty]7:-30 15:-20[/Penalty]
[ColorRed]220[/ColorRed]
[ColorGreen]0[/ColorGreen]
[ColorBlue]0[/ColorBlue]
[/PoliticalParty]

[PoliticalParty InternalName="Grey Brood"]
[ID]9[/ID]
[DisplayName]Grey Brood[/DisplayName]
[Model]gfx/Government/GreyBrood.png[/Model]
[OpposingParty]Red Brood[/OpposingParty]
[Bonus]8:20 4:20[/Bonus]
[Penalty]8:-20 4:-20[/Penalty]
[ColorRed]179[/ColorRed]
[ColorGreen]179[/ColorGreen]
[ColorBlue]179[/ColorBlue]
[/PoliticalParty]