Ballots for the Aug. 17 primary election are on their way to mailboxes across Clark County and beyond.The Clark County Elections Department mailed 218,162 primary ballots Wednesday, an all-time record, said elections supervisor Tim Likness. That tops the 216,000 ballots the county mailed for the 2008 general election, which decided a presidential race and several statewide contests. This year’s top two primary is a hot ballot, with contested races for the U.S. Senate, the open 3rd Congressional District seat and one open legislative seat in each of the 17th and 18th districts. The top two vote-getters in those races will compete in the general election regardless of their political party. In races with just two candidates, both will advance to the general election.County Auditor Greg Kimsey said turnout in primary elections has hovered between 36 percent and 38 percent since 2002, but predicted this year’s ballot return rate could reach 40 percent because of the number of competitive races on the ballot. The deadline for voter registration by mail already has passed, but people can register in person at the elections department, 1408 Franklin St., through Monday, Aug. 9.In addition to winnowing the candidate field in contests for federal and legislative offices, Clark County voters will pick the top two candidates for county assessor, county prosecuting attorney, state Supreme Court justice, Clark Public Utilities commissioner, and Vancouver city council.