The Nevada Supreme Court has ruled that the Democrats and Republicans can choose one candidate to run in the special election to fill the vacancy in the 2nd Congressional District. This election came about when Congressman Heller was named to replace resigned Senator Ensign.
In short the ruling says that the parties may each choose their nominee without a primary, which means the GOP candidate will be former State Senator Mark Amodei and the Democrats will run State Treasurer Kate Marshall.
Had there been a free for all with the chance for independent GOP candidates on the ballot the race would have been very competetive. But as it now stands the GOP has a clear edge, though you can never be sure in special elections.