USA Today is using Twitter as part of a cause-related marketing effort that will give one charity a full-page, full-color ad valued at nearly $190,000.

The Gannett-owned newspaper this week is encouraging Twitter users to post messages that include the hashtag #AmericaWants.

When the clock hits midnight at the end of the day on Friday, the nonprofit that receives the largest number of Tweets with the #AmericaWants tag will win the free ad.

If your group wants to take part, please take note of the following, because the rules of the contest are a bit tricky.

Unlike the recent #BeatCancer effort, which provided donations to a group of charities every time the #BeatCancer hashtag was used during a predetermined period, the USA Today contest requires users to do more than post a simple tag.

Users instead must post a full tweet that includes three elements: a hashtag, the name of the charity, and a message about the contest.

Each tweet must include “#AmericaWants (name of charity) to get a full-page ad in USA Today.”

So is the effort taking Twitter by storm?

Well, it hasn’t yet surplanted Twitter teen darling Justin Bieber from Twitter’s “Trending Topics” list.

But it does appear to have traction.

The newspaper’s Kindness blog reports celebrities such as Khloe Kardashian, Alyssa Milano, and Eva Longoria have tweeted messages as part of the contest. And during a recent 30-minute span the #AmericaWants hashtag was getting about eight tweets per minute.