Taylor Swift added a second show at Gillette Stadium after fans jammed phone lines for tickets to the country star’s July 27 show at Gillette Stadium. And if the response to this week’s pre-sale for members of Swift’s fan club is any indication, the country star should have no trouble selling out both shows. (The second show is July 26.) “The hottest ticket I’ve ever seen,” said someone who pays attention to such things. Of course, we already knew the appetite for country music was enormous around these parts after Jason Aldean managed to sell out two shows at Fenway Park in a matter of minutes. (The “Don’t You Wanna Stay?” singer is performing at the ballpark July 12 and 13.) Swift, who’s played at Gillette twice before, is promoting her new CD, “Red,” which sold over 1 million copies in its first week. It’s possible she’d add a third show at Gillette, but not likely, we’re told. Swift sold out two shows at Gillette on her “Speak Now” tour a year ago, becoming the first female solo act to headline the stadium, which seats 50,000 screaming fans. Tickets for the July 26 and 27 shows go on sale Saturday at 10 a.m. at ticketmaster.com.