The Porsche Carrera Cup GB title battle is shaping up to be a four-way contest over the second half of the season as teams and drivers head to North Yorkshire for rounds nine and ten at Croft (31 May/1 June).Just 28 points cover the top four drivers after the opening eight races and with 43 points on offer each weekend, the whole situation can change in one race. After the Croft weekend, there is a six-week mid-season break, so all the leading contenders will want to go into the break on the back of a strong weekend at Croft.Leading the championship, as he has done largely since the opening race at Brands Hatch at the end of March, is Michael Caine (Team Parker Racing). Caine took a double win that weekend to get his campaign off to a perfect start, and has been wracking up the points ever since. But for two doses of misfortune last time out at Thruxton, Caine could have a bigger points lead, for he was the quickest driver at the high-speed Hampshire track. However, a fourth and a fifth place finish was far less than he rightly expected at Thruxton and Caine needs to bounce back strongly at Croft to maintain the impetus of his title bid.Narrowly into second in the points at Thruxton came Caine's team mate Tim Bridgman, who has won four of the eight races to date. Brands was a disaster for the former single-seater champion, and he left Kent trailing Caine by a massive 41 points. In the space of three weekends, Bridgman has pegged the gap back to 16 points and will be eager to make further progress at Croft.For the fifth season on the trot, Tim Harvey is a major contender and heads the local Red Line Racing squad. A win at Croft would be perfect for both team and driver as Tim battles to win the Carrera Cup title that has so narrowly eluded him over recent seasons.Fourth of the title contenders at this stage of the season is Sam Hancock (Jota Sport) and a mighty double victory at Thruxton has catapulted Sam firmly into contention. The Jota Sport team is new to the Carrera Cup this season, but is rapidly making a big impression and Hancock clearly has the potential to challenge for the title over the second half of the season.However, this is not just about the big four drivers and two more contenders stand out as podium prospects. Phil Quaife, racing alongside Hancock at Jota Sport, is overdue another podium visit, while Charles Bateman (Team Parker Racing) has been the revelation of recent weekends, culminating in a mighty third in the most recent race at Thruxton.In the pro-am1 category, Yorkshire's Nigel Rice (Red Line Racing) has set the pace, but the consistency of Tony Gilham (ReDesign Racing) has given him a handy lead in the points. Meanwhile, adding further spice to the Croft entry will be young charger Stefan Hodgetts in the leading PCGB entry. Hodgetts, son of former BTCC champion Chris, has bags of natural talent and his progress in the Carrera Cup car will be watched with great interest.In the pro-am2 category, series newcomers Tommy Dreelan and Bob Lyons will join the grid in their pre-2008 911GT3 Cup Cars, racing alongside fellow Aberdeen resident Glynn Geddie, who will make his series debut in the PCGB entry.After qualifying on Saturday morning, the opening race will be on Saturday afternoon with the second race scheduled for 1.50pm on Sunday. The second race should feature in ITV4's live coverage of the BTCC action in a programme running from 12.30pm to 5.30pm.