MSSQL 2005+ supports direct quering xml columns as well as indexing them.
Thus you should be able to run your typical queries with slightly modified criteria for XML fields:
CREATE TABLE results_xml (pk INT PRIMARY KEY, FieldSQL XML not null)
insert into results_xml (pk,FieldSQL) values (1,'
<your_first_choice>Micheal D Higgins</your_first_choice>
,* from results_xml
FieldSQL.value('(/ResultsDS/Results/Your_Fifth_Choice)', 'nvarchar(1000)')='Barack Obama'
Syntax is not exact, as I do not have SQL Server running now.
More information can be found on MSDN:http://msdn.microsoft.com/en-us/library/ms345117(v=sql.90).aspx