By Alexandra Jaffe - 08/29/13 03:34 PM EDT
It comes on the heels of an attack launched by the Senate Conservatives Fund (SCF), a group that typically backs conservative primary challengers, charging that Alexander "refuses to join the fight" to defund the law because he's declined to sign on to a letter circulated by conservatives that effectively pledges to shut down the government if the law isn't defunded.
Alexander previously launched a radio ad touting his opposition to the healthcare law, but he's now turning to television to defend his record.
Conservatives believe he's vulnerable to a primary challenge and he has, in fact, already received one in state Rep. Joe Carr (R), who recently entered the race.
Carr is unlikely to gain much support from conservative groups, however, and SCF has indicated it's still looking for a candidate to endorse. But Alexander isn't taking the prospect of a primary challenge lightly, as evidenced by this new ad.
He also released internal polling earlier this week that shows him with a solid lead over four possible primary challengers, and with high job approval among GOP primary voters.
Watch the ad: