Hamilton is 52 points behind Alonso, with 25 earned each race. I know most people find it easier to visualize a mathematical situation in the championship with the old point system, so that’d be about 21 points with 10 points earned each race. There are 6 Grand Prix weekends left. Raikkonen overhauled Hamilton in 2007 with a 20 point deficiency in too, only 6 races, so it is plausible, but it will be extremely difficult for Lewis himself to do so.
The difference between the 2007 case and now are:
1.) Despite being a great championship, 2007 had very noncompetitive and dry racing, in normal race conditions no car came close to challenging Ferrari nor Mclaren, thus all what Raikkonen had to hope for was Hamilton misfortunes, which ultimately happened in the final 2 rounds of the championship.
2.) In 2012; we have Mclaren, Red Bull, Ferrari and Lotus as regular top runners with Mercedes, Sauber, Williams and Force occasionally challenging those four. A lot more drivers to take points off Alonso.
3.) Alonso is very consistent and the F2012, while not necessary the fastest car, is as reliable as a rock. As a team themselves too, Ferrari are rarely spoiling/losing points. Meanwhile, Mclaren, despite having a quicker car are constantly losing points due both their car being unreliable, and the team itself constantly making stupid/silly mistakes.