>I'm trying to run this query:
>
>

>DECLARE @voter_id INT
>SET @Command = 'SELECT @voter_id = voterid FROM tblCamp_CT WHERE VoterId = ' + CAST(@VoterId AS VARCHAR(20)) + ' AND ' + @Query
>EXEC (@Command)
>

>
>and I'm getting the error
>
>

>Must declare the scalar variable "@voter_id".
>

>
>What am I not seeing here???

Yes you didn't declare it :-)
The Dynamic SQL is executed in separate batch and any local variable declared in current batch is not visible there.
You must use sp_executesql:

DECLARE @voter_id INT
SET @Command = 'SELECT @voter_id = voterid FROM tblCamp_CT WHERE VoterId = ' + CAST(@VoterId AS VARCHAR(20)) + ' AND ' + @Query

EXEC sp_executesql @Command, N'@voter_id int OUTPUT', @voter_id = @voter_id OUTPUT