Of the ten House Republicans who voted to impeach former President Donald Trump, only two have survived their primaries to make it to the general election in November, each of them in states that use a top-two primary system.

Reps. David Valadao of California and Dan Newhouse of Washington advanced into the general election, running in two of the four states that use a top-two primary. Republican Sen. Lisa Murkowsi of Alaska, who voted to convict Trump in his second impeachment trial, advanced alongside Republican challenger Kelly Tshibaka, who campaigned with Trump, in a top-four ranked choice primary. (RELATED: Liz Cheney, After Losing By 37 Points, Says She Is ‘Thinking About’ A Presidential Run)

Republican Reps. Fred Upton of Michigan, Adam Kinzinger of Illinois, John Katko of New York and Anthony Gonzalez of Ohio all opted not to run at all this year. Peter Meijer of Michigan, Jaime Herrera Beutler of Washington, Tom Rice of South Carolina and Liz Cheney of Wyoming all lost their primaries to a Trump-endorsed opponent.

Valadao likely benefited from being the only impeachment supporter not facing a Trump-backed challenger, according to the San Francisco Chronicle. As a result of the primary containing two Trump supporters, voters who support the former president were split between two candidates, leading Valadao to edge out Chris Mathys by just 1,310 votes, the San Francisco Chronicle reported.

Newhouse also faced off against a pair of high-profile Trump supporters: Trump-endorsed Loren Culp and Navy veteran and retired NASCAR driver Jerrod Sessler, The New York Times reported. Newhouse, who narrowly came out on top of the crowded field ahead of Democratic businessman Dough White, raised $1.6 million, while Sessler had raised $508,900 and Culp just $310,700, the NYT reported.

Only three states use top-two primaries for congressional and state-level elections, with California, Nebraska and Washington using a top-two format and Alaska using a top-four variant, according to Ballotpedia. In a top-two primary format, all candidates are put on a ballot regardless of political affiliation, with the two candidates who acquire the most votes advance to the general election, according to Ballotpedia.

Alaska’s top-four variant follows the same principle but with the top four candidates advancing, and also uses a ranked choice format which allows voters to rank each candidate by preference, Ballotpedia reported. In this ranked choice system, voters rank candidates based on who they most prefer, with the candidate with the least support being eliminated and their supporters’ second choice votes added to the remaining candidates until a winner emerges, Politico reported.

Ranked choice voting in Alaska has been of particular interest, with advocates claiming that the system promotes campaigns focused on more positive messages, since they need to be listed as second and third choice by a significant number of voters, according to Politico.

“It immediately changed three things [in Minneapolis]: who decided to run, how campaigns were run and who could be elected,” said advocate James Massy to Politico, referring to the system’s impact on Minneapolis, where it has been used since 2009.

Spokespeople for Murkowski, Newhouse and Valadao did not immediately respond to a request for comment by the Daily Caller News Foundation.

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