Attach a form input to a node that will be submitted by multiple users
You can achieve that by the Webform module. or
Try the Simple Contest module

Simple Contest module provides contest system for Drupal websites.
Features:

contests are nodes. multiple contests of multiple contest type can be    run same time
Two winner types : Users &amp; Node, that means winners can be &quot;user&quot; or    node&quot;
multiple winners can be chosen by ranking/weight
Supports both automatic and manual winners selection
Winner chosen rule will be based on View. so it is up to you to    decide how the winner will be selected
Modules integration with Views, Token, Rules, Userpoints, Date    Repeat, Commerce Coupon, UC Gift Certificate &amp; UC Coupon
Token integration and customized E-mail notifications


Please note the this module is in dev version. So try that in local (test) environment.