June 22, 2015
Jeb Bush receives 22% support, more than any of the 15 other Republicans included in the latest NBC News / Wall Street Journal poll. Scott Walker received 17% and Marco Rubio 14%, while Ben Carson saw 11%. Other candidates receiving 5% or more included Mike Huckabee (9%), Rand Paul (7%) and Rick Perry (5%).
However: This is the first time Bush has exceeded 20% since early May when the last NBC News / Wall Street Journal poll gave him a similar 23%. In 9 intervening polls, conducted by a variety of organizations, Bush did not receive more than 15%. It is also worth noting that both of these polls have a very small sample size of about 250 Republicans, yielding a margin of error greater +/- 6%.
Who is right - NBC/WSJ or everyone else? We'll never really know since nobody is actually voting until early 2016 (and there is no national primary). 270toWin has a page that includes an average of the most recent Republican primary polls, and this shows Bush in a virtual tie with Walker, with Carson & Rubio tied for 3rd.