The latest Marist poll reveals that Mayor Bloomberg has opened up his lead against challenger City Comptroller Bill Thompson to 16 points amongst likely voters, with the incumbent receiving 52% to Thompson's 36%. Marist notes, "Last month, Bloomberg led Thompson among this group of voters by 9 percentage points — 52% to 43%, respectively. Although Bloomberg’s support is unchanged, Thompson has lost ground."

Marist also points out that Democratic voters have been shifting to Bloomberg: "Nearly half of Democrats — 47% — are planning to cast their ballot for Bloomberg while 39% are backing Thompson. Last month in a Marist survey conducted during the week of the Democratic primary, 51% supported Thompson, and 43% were behind Bloomberg." Here's the table for likely voters; f you look at Marist's table for registered voters, Bloomberg leads Thompson 47% to 38%.

At last count, Bloomberg had spent $65 million on his campaign advertising, while Thompson has reportedly spent 1/16 that.

Update: Thompson campaign spokeswoman Anne Fenton says:

"The key to this poll is that among the larger sample size of 744 NYC registered voters, the race is 47% for Mike Bloomberg and 38% for Bill Thompson - only a 9 point spread. Despite the nearly $100 million he has spent trying to buy this campaign, the Mayor is still under 50%, with 12% undecided. This is still a very open race and we are very optimistic.

The real numbers that New Yorkers are focused on are a 10.3 unemployment rate, 87% increase in property taxes, 98% increase in water rates and 1/3 of New Yorkers paying 50% of their monthly income on rent. Those are the numbers that New Yorkers will care about on November 3."