The Democratic candidate for U.S. Senate has erased the small gap between her and her Republican rival, and they were locked in a tie as they headed into their first debate Monday, a new poll showed.

Other polls also show the race neck-and-neck, and the contest to succeed retiring Democratic Sen. Bob Graham (search) is considered one of the top races that could help decide control of the Senate.

Mel Martinez (search), a Republican former member of President Bush's Cabinet, and Betty Castor (search), a Democratic former state education commissioner, each was the choice of 45 percent of respondents, according to the Mason-Dixon Polling & Research survey published Monday by several Florida media outlets. Nine percent were undecided.

A Mason-Dixon poll published Oct. 8 showed Martinez slightly ahead, 46 percent to 41 percent. Both polls had margins of sampling error of plus or minus 4 percentage points.

Castor and Martinez have been trading accusations over a former University of South Florida professor accused of supporting terrorists. Castor was president of the school while Sami Al-Arian taught there.

Martinez accused Castor of not doing enough to oust Al-Arian from her campus when the FBI first began investigating allegations that a think tank he founded there was a front for the Palestinian Islamic Jihad.

Castor countered with advertisements showing Al-Arian posing in 2000 with then-presidential candidate George W. Bush.

The most recent telephone poll was conducted Thursday through Saturday among 625 registered voters for The Miami Herald, The Tampa Tribune, Tallahassee Democrat and other media outlets.