So according to your desired workflow. You can follow these steps:

 1. Create a drupal form having two fields 'select candidate' and 'input
vote'.
 2. Now check if input vote < userpoint.
 3. And if yes on form submit record the vote and grant nominee points and deduct       from the logged in user. You can use
[form_rules][1] to trigger a rule on form submit or validate or
alternatively you can use [userpoints api][2] to grant or deduct
points.
 4. And if no , show the user a message that user don't have enough points.

So according to your desired workflow. You can follow these steps:

1. Create a drupal form having two fields 'select candidate' and 'input vote'.

2. Now check if input vote < userpoint.

3. And if yes on form submit record the vote and grant nominee points and deduct from the logged in user. You can use form_rules to trigger a rule on form submit or validate or alternatively you can use userpoints api to grant or deduct points.

4. And if no , show the user a message that user don't have enough points.