The Rasmussen Reports daily Presidential Tracking Poll for Tuesday shows—for the third time in four days--Barack Obama with a double digit lead in the race for the Democratic Presidential Nomination. Obama now attracts 51% of the vote while Hillary Clinton earns 40%. That’s the lowest total ever recorded for Clinton since the contest became a two-person race. Obama’s support has now been at or above 50% for four straight days. Prior to this stretch, he had reached the 50% level just once in more than a year of daily tracking polls.