In the first broad test of California’s new “top-two” election system, many candidates in heated races for Congress and the state Legislature have been campaigning earlier, spending more money and downplaying their party affiliation as they try to widen their appeal. Gone are the party primaries, except in the presidential race. Now all state candidates appear on a single ballot. Only those who come in first or second on June 5 will move on to the November general election, in which no write-in or other added candidates will be allowed. The new rules, approved by California voters in 2010, further empower voters who don’t belong to a political party _ already the fastest-growing category in California, accounting for more than 21 percent of the state’s registration.