NASHVILLE — Democrats say their presidential nominee, Barack Obama, can be competitive in Tennessee, but the most recent polling shows Republican John McCain’s widest lead in all 50 states can be found here. According to an Aug. 20 survey of 500 likely Tennessee voters by independent pollster Rasmussen Reports, Sen. McCain, R-Ariz., has opened a 24-point lead on Sen. Obama, D-Ill. Sen. McCain enjoyed a 56 percent to 32 percent edge in the poll, which had a 4.5 percent margin of error. The closest comparable state, according to state-by-state surveys listed on the Web site RealClearPolitics, is Kansas. There, an...