Once the two candidates clinched their respective party's nomination (McCain on March 4 and Obama on June 3), they turned their attention away from their competitors within their own party and toward one another.

However, there is one way in which the nominating conventions are still important -- at least for Republicans, this year -- Candidates who accept federal campaign funds must stop spending funds raised in the primary campaign when they accept their party's nomination.  Thus, McCain can no longer spend money raised for the primary campaign once he accepts his party's nomination.  However, Obama believes (and he is almost surely correct) that he can raise more money than the federal government provides.  When McCain accepts federal financing for his general election campaign he must also accept spending limits that will not constrain Obama.  Obama can spend any remaining primary funds after the Democratic convention, and he can spend as much money as he can raise.