What about the California recall election of 2003? Let's say Bustamante makes some egregious gaffe early on in the campaign ruling him out as the Democratic candidate, so the Democrats begin looking for another horse to rally around. Seeing the popularity of Schwarzenegger, they begin a search for their own celebrity candidate eventually finding one in Samuel L. Jackson.
Jackson runs an excellent campaign and for the sake of the scenario a few more Republicans stay in the race. Come the recall, Jackson wins a plurality of the votes (smaller than Arnie in OTL but enough to win) and becomes governor. Jackson's charisma is aided by a team of extremely talented advisors who work to get California out of trouble and back on it's feet.
Jackson wins again in 2006 and serves out his second term until 2011, conveniently leaving after financial troubles bring the GOP in a landslide election.
Butterflies prevent Jack Ryan's court records from leaking into the mainstream and so he manages a narrow victory over Barack Obama in 2004. Obama instead runs for a house seat in 2006 and wins. Come 2008, Hillary Clinton wins the Democratic Primary and goes on to lose a tight race to John McCain.
McCain's term in office is an unmitigated disaster. The Tea Party movement is just as strong if not stronger in TTL as it attempts to hijack the Republican Party. Very little actually gets done during McCain's 4 years in office and the Democrats eagerly look to 2012 to elect their candidate. Come the primaries numerous names are bandied about including Jackson's who has just recently finished his time in California. Jackson agrees to run and wins the Democratic nomination and goes on to defeat McCain in a landslide victory.