IN a behind-the-seams exclusive, designer Lela Rose gave The Post a sneak peek at two of the looks selected by Jenna and Barbara Bush to wear during their appearance at the Republican National Convention next month.

“They wanted to look smart without wearing a head-to-toe suited look,” says Rose, who declines to be labeled the first daughter’s “favorite” couturier.

“They wear clothes from many different designers,” she says firmly.

We bet Jenna’s choice (above right) – this elongated, olive wool-tweed jacket over a playful, tea-dyed short tulle dress – will generate plenty of buzz.

Barbara is going for all-out glamour in this sexy tulle dress strategically sequined (top left) – note to Alexandra Kerry! – to avoid any wardrobe malfunction.