Marsha Blackburn leads in the Republican U.S. Senate primary, Karl Dean leads in the Democratic gubernatorial primary, and Phil Bredesen probably would be leading in the Democratic U.S. Senate primary if he were a declared candidate, the latest MTSU Poll finds.

Meanwhile, nobody has established a clear lead in the Republican gubernatorial primary or the general-election races for governor and Senate.

"Some frontrunners seem to have emerged in some of the primary races, but it's much too early to forecast winners, even in the primaries that presently look lopsided," said Dr. Ken Blake, director of the poll at Middle Tennessee State University.

"All of these candidates have double-digit percentages of undecided voters, both among voters from their own parties and from across the Tennessee electorate as a whole. Any of the races easily could shift during the months ahead."

Here's a synopsis of the standings in each race, according to the poll:

• In the Republican primary for U.S. Senate, 55 percent of Republican voters approve or strongly approve of Blackburn, the representative for Tennessee's 7th Congressional District. Andy Ogles trails with 19 percent approval, as does Larry Crim, with 12 percent approval. Blackburn's lead is statistically significant, given the poll's error margin among self-identified Republicans.

• In the Democratic gubernatorial primary, former Nashville mayor Karl Dean has the approval of 49 percent of Democrats. The only other Democratic gubernatorial candidate considered in the poll, Craig Fitzhugh, drew a significantly smaller 26 percent approval.

• In the Democratic primary for U.S. Senate, 60 percent of Democratic voters approve or strongly approve of Bredesen, a former Tennessee governor. Thirty-two percent express such approval of Andy Berke, and 28 percent express such approval of James Mackler. Bredesen's lead is outside the error margin for the subgroup who self-identified as Democrats. But while both Bredesen and Berke have said they are thinking of running, neither man has declared himself a candidate. Mackler was the only declared Democratic candidate for Senate included in the poll.

• The Republican gubernatorial primary offers the least clarity for now. Diane Black, Tennessee's 6th Congressional District representative, led in the sample with 33 percent approval. But rival Republican Beth Harwell, speaker of the Tennessee House of Representatives, had the approval of a statistically indistinguishable 32 percent of the sample. Randy Boyd came in at 28 percent approval, and Mae Beavers at 21 percent approval. But the poll's error margin for self-described Republican voters was too wide to indicate which, if any, of these candidates was leading the pack. The poll could determine only that Bill Lee, at 15 percent approval among Republicans, was significantly behind the approval ratings for Harwell and Black.

• In the race for Tennessee governor among all Tennessee voters - Democrats, Republicans, independents and others - Harwell, a Republican, and Dean, a Democrat, both attract 23 percent approval, followed closely by three Republicans: Black, at 22 percent approval; Boyd, at 17 percent approval; and Beavers, at 15 percent approval. The poll's overall error margin of 4 percentage points could not estimate which, if any, of these candidates was ahead. It could, however, identify the remaining two candidates, Fitzhugh and Lee, as significantly trailing Harwell, Dean and Black.

• Finally, in the race for U.S. Senate among all Tennessee voters, approval for Blackburn, a Republican, stands at 37 percent, statistically indistinguishable from approval of Bredesen, a Democrat, at 34 percent. Both polled significantly higher on approval than did Berke (18 percent), Ogles (14 percent), Mackler (13 percent), and Crim (7 percent).

All results are based on questions that presented the declared or potential candidates for each race one at a time, in a random order, and asked whether the respondent strongly favored, favored, neither favored nor opposed, opposed, or strongly opposed that person's being elected. The U.S. Senate results did not include results for Republican Stephen Fincher, who declared his candidacy near the end of the poll's field period and too late to gather meaningful data about attitudes toward him.

Based on interviews with 600 registered Tennessee voters reached via randomly selected cell and landline phone numbers, the scientifically valid poll was conducted Oct. 16-23 and has an error margin of plus-or-minus 4 percentage points.